SCJP模拟题

数据加载中……

scjp模拟试题（一）

Question No: 1
1.public class test (
2. public static void main (String args[]) {
3. int i = 0xFFFFFFF1;
4. int j = ~i;
5.
6. }
7. )
What is the decimal value of j at line 5?
A. 0
B. 1
C. 14
D. –15
E. An error at line 3 causes compilation to fail.
F. An error at line 4 causes compilation to fail.
答案: C

Question No: 2
Given:
Integer i = new Integer (42);
Long 1 = new Long (42);
Double d = new Double (42.0);
Which two expressions evaluate to True? (Choose Two)
A. (i ==1)
B. (i == d)
C. (d == 1)
D. (i.equals (d))
E. (d.equals (i))
F. (i.equals (42))
答案: D, E

Question No: 3
Exhibit :
1. public class test (
2. private static int j = 0;
3.
4. private static boolean methodB(int k) (
5. j += k;
6. return true;
6. )
7.
8. public static void methodA(int i) {
9. boolean b:
10. b = i < 10 | methodB (4);
11. b = i < 10 || methodB (8);
12. }
13.
14. public static void main (String args[] ) (
15. methodA (0);
16. system.out.printIn(j);
17. )
18. )
What is the result?
A. The program prints “0”
B. The program prints “4”
C. The program prints “8”
D. The program prints “12”
E. The code does not complete.
答案: B

Question No: 4
Given
1. Public class test (
2. Public static void main (String args[]) (
3. System.out.printIn (6 ^ 3);
4. )
5. )
What is the output?
答案: 5

Question No: 5
Given:
1. public class Foo {
2. public static void main (String [] args) {
3. StringBuffer a = new StringBuffer (“A”);
4. StringBuffer b = new StringBuffer (“B”);
5. operate (a,b);
6. system.out.printIn{a + “,” +b};
7. }
8. static void operate (StringBuffer x, StringBuffer y) {
9. x.append {y};
10. y = x;
11. }
12. }
What is the result?
A. The code compiles and prints “A,B”.
B. The code compiles and prints “A,A”.
C. The code compiles and prints “B,B”.
D. The code compiles and prints “AB,B”.
E. The code compiles and prints “AB,AB”.
F. The code does not compile because “+” cannot be overloaded for StringBuffer.
答案: D

Question No: 6
Exhibit:
1. Public class test (
2. Public static void stringReplace (String text) (
3. Text = text.replace (‘j’ , ‘i’);
4. )
5.
6. public static void bufferReplace (StringBuffer text) (
7. text = text.append (“C”)
8. )
9.
10. public static void main (String args[]) (
11. String textString = new String (“java”);
12. StringBuffer text BufferString = new StringBuffer (“java”);
13.
14. stringReplace (textString);
15. BufferReplace (textBuffer);
16.
17. System.out.printIn (textString + textBuffer);
18. )
19. )
What is the output?
答案: JAVAJAVA

Question No: 7
Exhibit:
1. public class test {
2. public static void add3 (Integer i) }
3. int val = i.intValue ( );
4. val += 3;
5. i = new Integer (val);
6. )
7.
8. public static void main (String args [ ] ) {
9. Integer i = new Integer (0);
10. add3 (i);
11. system.out.printIn (i.intValue ( ) );
12. }
13. )
What is the result?
A. Compilation will fail.
B. The program prints “0”.
C. The program prints “3”.
D. Compilation will succeed but an exception will be thrown at line 3.
答案: B

Question No: 8
Given:
1. public class ConstOver {
2. public ConstOver (int x, int y, int z) {
3. }
4. }
Which two overload the ConstOver constructor? (Choose Two)
A. ConstOver ( ) { }
B. Protected int ConstOver ( ) { }
C. Private ConstOver (int z, int y, byte x) { }
D. Public Object ConstOver (int x, int y, int z) { }
E. Public void ConstOver (byte x, byte y, byte z) { }
答案: A, C

Question No: 9
Given:
1. public class MethodOver {
2. public void setVar (int a, int b, float c) {
3. }
4. }
Which two overload the setVar method? (Choose Two)
A. Private void setVar (int a, float c, int b) { }
B. Protected void setVar (int a, int b, float c) { }
C. Public int setVar (int a, float c, int b) (return a;)
D. Public int setVar (int a, int b, float c) (return a;)
E. Protected float setVar (int a, int b, float c) (return c;)
答案: A, C

Question No: 10
Given:
1. class BaseClass {
2. Private float x = 1.0f ;
3. protected float getVar ( ) ( return x;)
4. }
5. class Subclass extends BaseClass (
6. private float x = 2.0f;
7. //insert code here
8. )
Which two are valid examples of method overriding? (Choose Two)
A. Float getVar ( ) { return x;}
B. Public float getVar ( ) { return x;}
C. Float double getVar ( ) { return x;}
D. Public float getVar ( ) { return x;}
E. Public float getVar (float f ) { return f;}
答案: B, D

Question No: 11
Which two demonstrate an “is a” relationship? (Choose Two)
A. public interface Person { }
public class Employee extends Person { }
B. public interface Shape { }
public class Employee extends Shape { }
C. public interface Color { }
public class Employee extends Color { }
D. public class Species { }
public class Animal (private Species species;)
E. interface Component { }
Class Container implements Component (
Private Component[ ] children;
)
答案: D, E

Question No: 12
Which statement is true?
A. An anonymous inner class may be declared as final.
B. An anonymous inner class can be declared as private.
C. An anonymous inner class can implement multiple interfaces.
D. An anonymous inner class can access final variables in any enclosing scope.
E. Construction of an instance of a static inner class requires an instance of the enclosing outer class.
答案: D

Question No 13
Given:
1. package foo;
2.
3. public class Outer (
4. public static class Inner (
5. )
6. )
Which statement is true?
A. An instance of the Inner class can be constructed with “new Outer.Inner ()”
B. An instance of the inner class cannot be constructed outside of package foo.
C. An instance of the inner class can only be constructed from within the outer class.
D. From within the package bar, an instance of the inner class can be constructed with “new inner()”
答案: A

Question No 14
Exhibit:
1. public class enclosingone (
2. public class insideone{}
3. )
4. public class inertest(
5. public static void main (string[]args)(
6. enclosingone eo= new enclosingone ();
7. //insert code here
8. )
9. )
Which statement at line 7 constructs an instance of the inner class?
A. InsideOnew ei= eo.new InsideOn();
B. Eo.InsideOne ei = eo.new InsideOne();
C. InsideOne ei = EnclosingOne.new InsideOne();
D. EnclosingOne.InsideOne ei = eo.new InsideOne();
答案: D

Question No 15
Exhibit:
1. interface foo {
2. int k = 0;
3. }
4.
5. public class test implements Foo (
6. public static void main(String args[]) (
7. int i;
8. Test test = new test ();
9. i= test.k;
10.i= Test.k;
11.i= Foo.k;
12.)
13.)
14.
What is the result?
A. Compilation succeeds.
B. An error at line 2 causes compilation to fail.
C. An error at line 9 causes compilation to fail.
D. An error at line 10 causes compilation to fail.
E. An error at line 11 causes compilation to fail.
答案: A

Question No 16
Given:
1. //point X
2. public class foo (
3. public static void main (String[]args) throws Exception {
4. printWriter out = new PrintWriter (new
5. java.io.outputStreamWriter (System.out), true;
6. out.printIn(“Hello”);
7. )
8. }
Which statement at PointX on line 1 allows this code to compile and run?
A. Import java.io.PrintWriter;
B. Include java.io.PrintWriter;
C. Import java.io.OutputStreamWriter;
D. Include java.io.OutputStreamWriter;
E. No statement is needed.
答案: A

Question No 17
Which two statements are reserved words in Java? (Choose Two)
A. Run
B. Import
C. Default
D. Implement
答案: B, C

Question No 18
Which three are valid declarations of a float? (Choose Three)
A. Float foo = -1;
B. Float foo = 1.0;
C. Float foo = 42e1;
D. Float foo = 2.02f;
E. Float foo = 3.03d;
F. Float foo = 0x0123;
答案: A, D, F

Question No 19
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Question No 19
Given:
8. int index = 1;
9. boolean[] test = new Boolean[3];
10. boolean foo= test [index];
What is the result?
A. Foo has the value of 0.
B. Foo has the value of null.
C. Foo has the value of true.
D. Foo has the value of false.
E. An exception is thrown.
F. The code will not compile.
答案: D

Question No 20
Given:
1. public class test(
2. public static void main(string[]args){
3. string foo = args [1];
4. string foo = args [2];
5. string foo = args [3];
6. }
7. )
And command line invocation:
Java Test red green blue
What is the result?
A. Baz has the value of “”
B. Baz has the value of null
C. Baz has the value of “red”
D. Baz has the value of “blue”
E. Bax has the value of “green”
F. The code does not compile.
G. The program throws an exception.
答案: G

Question No 21
Given:
8. int index = 1;
9. int [] foo = new int [3];
10.int bar = foo [index];
11.int baz = bar + index;
What is the result?
A. Baz has the value of 0
B. Baz has the value of 1
C. Baz has the value of 2
D. An exception is thrown.
E. The code will not compile.
答案: B

Question No 22
Given:
1. public class foo {
2. public static void main (String[]args) {
3. String s;
4. system.out.printIn (“s=” + s);
5. }
6. }
What is the result?
A. The code compiles and “s=” is printed.
B. The code compiles and “s=null” is printed.
C. The code does not compile because string s is not initialized.
D. The code does not compile because string s cannot be referenced.
E. The code compiles, but a NullPointerException is thrown when toString is called.
答案: C

Question No 23
Which will declare a method that forces a subclass to implement it?
A. Public double methoda();
B. Static void methoda (double d1) {}
C. Public native double methoda();
D. Abstract public void methoda();
E. Protected void methoda (double d1){}
答案: D

Question No 24
You want subclasses in any package to have access to members of a superclass. Which is the most
restrictive access modifier that will accomplish this objective?
A. Public
B. Private
C. Protected
D. Transient
E. No access modifier is qualified
答案: C

Question No 25
Given:
1. abstract class abstrctIt {
2. abstract float getFloat ();
3. }
4. public class AbstractTest extends AbstractIt {
5. private float f1= 1.0f;
6. private float getFloat () {return f1;}
7. }
What is the result?
A. Compilation is successful.
B. An error on line 6 causes a runtime failure.
C. An error at line 6 causes compilation to fail.
D. An error at line 2 causes compilation to fail.
答案: C

Question No 26
Exhibit:
1. public class test(
2. public int aMethod()[
3. static int i=0;
4. i++;
5. return I;
6. ]
7. public static void main (String args[]){
8. test test = new test();
9. test.aMethod();
10.int j = test.aMethod();
11.System.out.printIn(j);
12.}
13.)
What is the result?
A. Compilation will fail.
B. Compilation will succeed and the program will print “0”
C. Compilation will succeed and the program will print “1”
D. Compilation will succeed and the program will print “2”
答案: D

Question No 27
Given:
1. class super {
2. public float getNum() {return 3.0f;}
3. }
4.
5. public class Sub extends Super {
6.
7. }
Which method, placed at line 6, will cause a compiler error?
A. Public float getNum() {return 4.0f; }
B. Public void getNum () { }
C. Public void getNum (double d) { }
D. Public double getNum (float d) {retrun 4.0f; }
答案: B

Question No 28
Which declaration prevents creating a subclass of an outer class?
A. Static class FooBar{}
B. Private class FooBar{}
C. Abstract public class FooBar{}
D. Final public class FooBar{}
E. Final abstract class FooBar{}
答案: D

Question No 29
Given:
1. byte [] arry1, array2[];
2. byte array3 [][];
3. byte[][] array4;
If each array has been initialized, which statement will cause a compiler error?
A. Array2 = array1;
B. Array2 = array3;
C. Array2 = array4;
D. Both A and B
E. Both A and C
F. Both B and C
答案: F

Question No 30
Exhibit:
1. class super (
2. public int I = 0;
3.
4. public super (string text) (
5. I = 1
6. )
7. )
8.
9. public class sub extends super (
10. public sub (string text) (
11. i= 2
12. )
13.
14. public static void main (straing args[]) (
15. sub sub = new sub (“Hello”);
16. system.out. PrintIn(sub.i);
17. )
18. )
What is the result?
A. Compilation will fail.
B. Compilation will succeed and the program will print “0”
C. Compilation will succeed and the program will print “1”
D. Compilation will succeed and the program will print “2”
答案: A

Question No 31
Given:
1. public class returnIt (
2. returnType methodA(byte x, double y) (
3. return (short) x/y * 2;
4. )
5. )
What is the valid returnType for methodA in line 2?
A. Int
B. Byte
C. Long
D. Short
E. Float
F. Double
答案: F

Question No 32
Given the ActionEvent, which method allows you to identify the affected component?
A. GetClass.
B. GetTarget.
C. GetSource.
D. GetComponent.
E. GetTargetComponent.
答案: C

Question No 33
Which is a method of the MouseMotionListener interface?
A. Public void mouseMoved(MouseEvent)
B. Public boolean mouseMoved(MouseEvent)
C. Public void mouseMoved(MouseMotionEvent)
D. Public boolean MouseMoved(MouseMotionEvent)
E. Public boolean mouseMoved(MouseMotionEvent)
答案: A

Question No 34
Exhibit:
1. import java.awt*;
2.
3. public class X extends Frame (
4. public static void main(string []args) (
5. X x = new X ();
6. X.pack();
7. x.setVisible(true);
8. )
9.
10. public X () (
11. setlayout (new GridLayout (2,2));
12.
13. Panel p1 = new panel();
14. Add(p1);
15. Button b1= new Button (“One”);
16. P1.add(b1);
17.
18. Panel p2 = new panel();
19. Add(p2);
20. Button b2= new Button (“Two”);
21. P2.add(b2);
22.
23. Button b3= new Button (“Three”);
24. add(b3);
25.
26. Button b4= new Button (“Four”);
27. add(b4);
28. )
29. )
Which two statements are true? (Choose Two)
A. All the buttons change height if the frame height is resized.
B. All the buttons change width if the Frame width is resized.
C. The size of the button labeled “One” is constant even if the Frame is resized.
D. Both width and height of the button labeled “Three” might change if the Frame is resized.
答案: C, D

Question No 35
You are assigned the task of building a panel containing a TextArea at the top, a label directly below it,
and a button directly below the label. If the three components are added directly to the panel. Which
layout manager can the panel use to ensure that the TextArea absorbs all of the free vertical space when
the panel is resized?
A. GridLayout.
B. CardLayout.
C. FlowLayout.
D. BorderLayout.
E. GridBagLayout.
答案: E

Question No 36
Which gets the name of the parent directory file “file.txt”?
A. String name= File.getParentName(“file.txt”);
B. String name= (new File(“file.txt”)).getParent();
C. String name = (new File(“file.txt”)).getParentName();
D. String name= (new File(“file.txt”)).getParentFile();
E. Directory dir=(new File (“file.txt”)).getParentDir();
String name= dir.getName();
答案: B

Question No 37
Which can be used to encode charS for output?
A. Java.io.OutputStream.
B. Java.io.OutputStreamWriter.
C. Java.io.EncodeOutputStream.
D. Java.io.EncodeWriter.
E. Java.io.BufferedOutputStream.
答案: B

Question No 38
The file “file.txt” exists on the file system and contsins ASCII text.
Given:
38. try {
39. File f = new File(“file.txt”);
40. OutputStream out = new FileOutputStream(f, true);
41. }
42. catch (IOException) {}
What is the result?
A. The code does not compile.
B. The code runs and no change is made to the file.
C. The code runs and sets the length of the file to 0.
D. An exception is thrown because the file is not closed.
E. The code runs and deletes the file from the file system.
答案: A

Question No 39
Which constructs a DataOutputStream?
A. New dataOutputStream(“out.txt”);
B. New dataOutputStream(new file(“out.txt”));
C. New dataOutputStream(new writer(“out.txt”));
D. New dataOutputStream(new FileWriter(“out.txt”));
E. New dataOutputStream(new OutputStream(“out.txt”));
F. New dataOutputStream(new FileOutputStream(“out.txt”));
答案: F

Question No 40
What writes the text “” to the end of the file “file.txt”?
A. OutputStream out= new FileOutputStream (“file.txt”);
Out.writeBytes (“/n”);
B. OutputStream os= new FileOutputStream (“file.txt”, true);
DataOutputStream out = new DataOutputStream(os);
out.writeBytes (“/n”);
C. OutputStream os= new FileOutputStream (“file.txt”);
DataOutputStream out = new DataOutputStream(os);
out.writeBytes (“/n”);
D. OutputStream os= new OutputStream (“file.txt”, true);
DataOutputStream out = new DataOutputStream(os);
out.writeBytes (“/n”);
答案: B

Question No 41
Given:
1. public class X (
2. public object m () {
3. object o = new float (3.14F);
4. object [] oa = new object [1];
5. oa[0]= o;
6. o = null;
7. return oa[0];
8. }
9. )
When is the float object created in line 3, eligible for garbage collection?
A. Just after line 5
B. Just after line 6
C. Just after line 7 (that is, as the method returns)
D. Never in this method.
答案: D

Question No 42
Given:
3. string foo = “ABCDE”;
4. foo.substring(3);
5. foo.concat(“XYZ”);
6.
Type the value of foo at line 6.
答案: ABCDE

Question No 43
Which method is an appropriate way to determine the cosine of 42 degrees?
A. Double d = Math.cos(42);
B. Double d = Math.cosine(42);
C. Double d = Math.cos(Math.toRadians(42));
D. Double d = Math.cos(Math.toDegrees(42));
E. Double d = Math.cosine(Math.toRadians(42));
答案: C

Question No 44
You need to store elements in a collection that guarantees that no duplicates are stored and all elements
can be accessed in natural order. Which interface provides that capability?
A. Java.util.Map.
B. Java.util.Set.
C. Java.util.List.
D. Java.util.StoredSet.
E. Java.util.StoredMap.
F. Java.util.Collection.
答案: D

Question No 45
Which statement is true for the class java.util.HashSet?
A. The elements in the collection are ordered.
B. The collection is guaranteed to be immutable.
C. The elements in the collection are guaranteed to be unique.
D. The elements in the collection are accessed using a unique key.
E. The elements in the collections are guaranteed to be synchronized.
答案: C

Question No 46
Given:
1. public class IfTest (
2. public static void main(string[]args) {
3. int x = 3;
4. int y = 1;
5. if (x = y)
6. system.out.printIn(“Not equal”);
7. else
8. system.out.printIn(“Equal”);
9. }
10. )
What is the result?
A. The output is “Equal”
B. The output in “Not Equal”
C. An error at line 5 causes compilation to fall.
D. The program executes but does not print a message.
答案: C

Question No 47
Exhibit:
1. public class test (
2. public static void main(string args[]) {
3. int 1= 0;
4. while (i) {
5. if (i==4) {
6. break;
7. }
8. ++i;
9. }
10.
11. }
12. )
What is the value of i at line 10?
A. 0
B. 3
C. 4
D. 5
E. The code will not compile.
答案: E

Question No 48
Given:
3. int i= 1, j= 10 ;
4. do (
5. if (i++> --j) continue;
6. ) while (i<5);
After execution, what are the values for I and j?
A. i = 6 and j= 5
B. i = 5 and j= 5
C. i = 6 and j= 4
D. i = 5 and j= 6
E. i = 6 and j= 6
答案: D

Question No 49
Given:
1. switch (i) {
2. default:
310-025
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- 27 -
3. System.out.printIn(“Hello”);
4. }
What are the two acceptable types for the variable i? (Choose Two)
A. Char
B. Byte
C. Float
D. Double
E. Object
答案: A, B

Question No 50
Given:
1. public class foo {
2. public static void main (string[]args)
3. try {return;}
4. finally {system.out.printIn(“Finally”);}
5. }
6. }
What is the result?
A. The program runs and prints nothing.
B. The program runs and prints “Finally”
C. The code compiles, but an exception is thrown at runtime.
D. The code will not compile because the catch block is missing.
答案: B

Question No 51
51. Which correctly create an array of five empty Strings?
A. String a[] = new String[5];
for (int i=0;i<5;a[i++]=””);
B. String a []={“”,””,””,””,””};
C. String a[5];
D. String [5] a;
E. String [] a = new String[5];
for (int i = 0 ;i<5;a[i++] = null);
答案:A、B

Question No 52
52. Which cannot be added to a Container?
A. an Applet
B. a Component
C. a Container
D. a MenuComponent
E. a panel
答案:D

Question No 53
53. Which is the return value of Event listener?s method?
A. String B. AWTEvent C. void D. int
答案:C

Question No 54
54. If we implements MouseListener, which is corrected argument of its method? (short answer)
答案: MouseEvent

Question No 55
55. Use the operator “>>” and “>>>”. Which statement is true?
A. 1010 0000 0000 0000 0000 0000 0000 0000 >> 4 give
0000 1010 0000 0000 0000 0000 0000 0000
B. 1010 0000 0000 0000 0000 0000 0000 0000 >> 4 give
1111 1010 0000 0000 0000 0000 0000 0000
C. 1010 0000 0000 0000 0000 0000 0000 0000 >>> 4 give
0000 1010 0000 0000 0000 0000 0000 0000
D. 1010 0000 0000 0000 0000 0000 0000 0000 >>> 4 give
1111 1010 0000 0000 0000 0000 0000 0000
答案: B、C

Question No 56
56. Give following fragment.
Outer: for(int i=0; i<3; i++)
inner:for(int j=0;j<3;j++){
If(j>1)break outer;
System.out.println(j+”and”+i);
}
Which will be output?
A. 0 and 0 B. 0 and 1 C. 0 and 2 D. 0 and 3
E. 1 and 0 F. 1 and 1 G. 1 and 2 H. 1 and 3
I. 2 and 0 J. 2 and 1 K. 2 and 2 L. 2 and 3
答案: A、E

Question No 57
57. Examine the following code which includes an inner class:
public final class Test4 implements A{
class Inner{
void test(){
if (Test4.this.flag);{
sample();
}
}
private boolean flag=false;
}
public void sample(){
System.out.println(“Sample”);
}
public Test4(){
(new Inner()).test();
}
public static void main(String args[]){
new Test4();
}
}
What is the result:
A.Print out “Sample”
B.Program produces no output but termiantes correctly.
C. Program does not terminate.
D.The program will not compile
答案:A

Question No 58
58. What is written to the standard output given the following statement:
System.out.println(4|7);
Select the right answer:
A.4
B.5
C.6
D.7
E.0
答案:D

Question No 59
59. Look the inheritance relation:
person
|
----------------
| |
man woman
In a source of java have the following line:
person p=new man();
What statement are corrected?
A. The expression is illegal.
B. Compile corrected but running wrong.
C. The expression is legal.
D. Will construct a person?s object.
答案:C

Question No 60
60. Look the inheritance relation:
person
|
----------------
| |
man woman
In a source of java have the following line:
woman w=new man():

What statement are corrected?
A. The expression is illegal.
B. Compile corrected but running wrong.
C. The expression is legal.
D. Will construct a woman object.
答案:A

Question No 61
61． Which can NOT be used in declaring or declaring and initializing an automatic (method local) variable?
A. final
B. static
C. expressions
D. Constants of non-primitive type
E. initialized arrays (such as “ {“Hello”,”Good bye”}”).
答案:B

scjp模拟试题（二）

Question No: 1
public class test (
2. public static void main (String args[]) {
3. int i = 0xFFFFFFF1;
4. int j = ~i;
5.
6. }
7. )
What is the decimal value of j at line 5?
A. 0
B. 1
C. 14
D. –15
E. An error at line 3 causes compilation to fail.
F. An error at line 4 causes compilation to fail.
答案: C

Question No: 4
Given
1. Public class test (
2. Public static void main (String args[]) (
3. System.out.printIn (6 ^ 3);
4. )
5. )
What is the output?
答案: 5

Question No 17
Which two statements are reserved words in Java? (Choose Two)
A. Run
B. Import
C. Default
D. Implement
答案: B, C

Question No 32
Given the ActionEvent, which method allows you to identify the affected component?
A. GetClass.
B. GetTarget.
C. GetSource.
D. GetComponent.
E. GetTargetComponent.
答案: C

Question No 42
Given:
3. string foo = “ABCDE”;
4. foo.substring(3);
5. foo.concat(“XYZ”);
6.
Type the value of foo at line 6.
答案: ABCDE

Question No 51
51． Given the following incomplete method:
1) public void method(){
2}
3} if (someTestFails()){
4}
5} }
6}
7} }
You want to make this method throw an IOException if,and only if,the method someTestFails() returns a value of true.
Which changes achieve this?
A. Add at line 2:IOException e;
B. Add at line 4:throw e;
C. Add at line 4:throw new IOException();
D. Add at line 6:throw new IOException();
E. Modify the method declaration to indicate that an object of type Exception might be thrown.
答案: C、E

Question No 52
52． Given the following definition:
String s = null;
Which code fragments cause an object of type NullPointerException to be thrown?
A. if((s!=null)&(s.length()>0))
B. if((s!=null)&&(s.length()>0))
C. if((s==null)|(s.length()==0))
D. if((s==null)||(s.length()==0))

答案: A、C

Question No 53
53． The following is a program
1) class Exsuper{
2} String name;
3} String nick_name;
4}
5} public ExSuper(String s,String t){
6} name = s;
7} nick_name = t;
8} }
9}
10} public string toString(){
11} return name;
12} }
13} }
14)
15) public class Example extends ExSuper{
16}
17} public Example(String s,String t){
18} super(s,t);
19} }
20}
21} public String to String(){
22} return name +”a.k.a”+nick_name;
23} }
24}
25} public static void main(String args[]){
26} ExSuper a = new ExSuper(“First”,”1st”);
27} ExSuper b = new Example(“Second”,”2nd”);
28}
29} System.out.println(“a is”+a.toString());
30} System.out.println(“b is”+b.toString());
31} }
32} }
What happens when the user attempts to compile and run this program?
` A. A Compiler error occurs at line 21
B. An object of type ClassCastException is thrown at line 27
C.The following output:
a is First
b is second
D. The following output:
a is First
b is Secong a.k.a 2nd
F. The following output:
a is First a.k.a 1st
b is Second a.k.a 2nd
答案:D

Question No 54
54． Which statements are true about Listeners?
A. At most one listener can be added to any simple Component.
B. The return value from a listener is used to control the invocation of other listener
C. If multiple listeners are added to a single component, they must all be made friends to each other
D. If multiple listeners are added to single component, the order of invocation of the listener is not specified.
E. In the AWT, listener methods generally take an argument, which is an instance of some subclass of java.awt.AWTEvent class.
答案: D、E

Question No 55
55． Given the following class outline:
class Example{
private int x;
// rest of class body
public static void main(String args[]){
//implementation of main mehtod}
}
Which statement is true?
A. x=2 is a valid assignment in the main() method of class Example.
B. Changing private int x to int x would make x=2 a valid assignment in the main() method of class Example.
C. Changing private int x to public int x would make x=2 a valid assignment in the main() method of class Example.
D. Changing private int x to static int x would make x=2 a valid assignment in the main() method of class Example.
E. Changing class Example to public class Example would make x=2 a valid assignment in the main() method of class Example.
答案:D

Question No 56
56． Which statement is true about an inner class?
A. It must be anonymous
B. It can not implement an interface
C. It is only accessible in the enclosing class
D. It can access any final variables in any enclosing scope.
答案:D

Question No 57
57． Which statement is true about the grid bag layout manager?
A. The number of rows and columns is fixed when the container is created.
B. The number of rows and columns is fixed when the GridBagLayout object is created.
C. If a component has a fill value of BOTH, then as the container change size, the component is resized.
D. Every component must carry a non-zero weightx and weighty value when it is added to the container
E. If a row has a weighty value that is non-zero, then as the container changes height, the row changes height.
答案:C

Question No 58
58． Which statement are true about writing a class that is to handle the events issued by a user interface component.
A. Subclassing an adapter is inappropriate in this case.
B. The class should implement some listener interface
C. A class can implement multiple listener interfaces if desired.
D. A subclass of an AWT component cannot listen to its own events.
E. When implements listener interface, a class need only provide those handler methods that it chooses.
答案: B、C

Question No 59
59．The argument for a class?s main() method is called args, and the class is invoked as follows.
java Example cat
What would be the effect of trying to access args[0] in the main method?
A. The value produced is cat
B. The value produced is java
C. The value produced is Example
D. An object of type NullPointerException is thrown.
E. An object of type ArrayIndexOutofBoundsException is thrown.
答案:A

Question No 60
60． Which best describes the requirements of a fully encapsulated class?
A. Mehtods must not be private.
B. Variables must not be public.
C. The class must be marked final
D. Public methods are all marked final.
E. Modification of the objects state is only possible using method calls.
答案:E

Question No 61
61．Which contains objects without ordering, duplication, or any particular lookup/retrieval mechanism?
A. Map
B. Set
C. List
D. Collection
E. Enumeration
答案:B

scjp模拟试题（三）

Question No: 1
1.Which statement about the garbage collection mechanism are true?
A. Garbage collection require additional programe code in cases where multiple threads are running.
B. The programmer can indicate that a reference through a local variable is no longer of interest.
C. The programmer has a mechanism that explicity and immediately frees the memory used by Java objects.
D. The garbage collection mechanism can free the memory used by Java Object at explection time.
E. The garbage collection system never reclaims memory from objects while are still accessible to running user threads.
答案:B、E

Question No: 2
2. Give the following method:
1) public void method( ){
2} String a,b;
3} a=new String(“hello world”);
4} b=new String(“game over”);
5} System.out.println(a+b+”ok”);
6} a=null;
7} a=b;
8} System.out.println(a);
9} }
In the absence of compiler optimization, which is the earliest point the object a refered is definitely elibile to be garbage collection.
A. before line 3
B.before line 5
C. before line 6
D.before line 7
E. Before line 9
答案:D

Question No: 3
3. In the class java.awt.AWTEvent,which is the parent class upon which jdk1.1 awt events are based there is a method called getID which phrase accurately describes the return value of this method?
A. It is a reference to the object directly affected by the cause of the event.
B. It is an indication of the nature of the cause of the event.
C. It is an indication of the position of the mouse when it caused the event.
D. In the case of a mouse click, it is an indication of the text under the mouse at the time of the event.
E. It tells the state of certain keys on the keybord at the time of the event.
F. It is an indication of the time at which the event occurred.
答案: B

Question No: 4
4. Which statement about listener is true?
A. Most component allow multiple listeners to be added.
B. If multiple listener be add to a single component, the event only affected one listener.
C. Component don?t allow multiple listeners to be add.
D. The listener mechanism allows you to call an addXxxxListener method as many times as is needed, specifying as many different listeners as your design require.
答案: A、D

Question No: 5
5.Give the following code:
public class Example{
public static void main(String args[] ){
int l=0;
do{
System.out.println(“Doing it for l is:”+l);
}while(--l>0)
System.out.println(“Finish”);
}
}
Which well be output:
A. Doing it for l is 3
B. Doing it for l is 1
C. Doing it for l is 2
D. Doing it for l is 0
E. Doing it for l is ?C1
F. Finish
答案: D、F

Question No: 6
6. Give the code fragment:
1) switch(x){
2} case 1:System.out.println(“Test 1”);break;
3} case 2:
4} case 3:System.out.println(“Test 2”);break;
5} default:System.out.println(“end”);
6} }
which value of x would cause “Test 2” to the output:
A. 1
B. 2
C. 3
D. default
答案: B.C

Question No: 7
7. Give incompleted method:
1)
2) { if(unsafe()){//do something…}
3} else if(safe()){//do the other…}
4} }
The method unsafe() well throe an IOException, which completes the method of declaration when added at line one?
A. public IOException methodName()
B. public void methodName()
C. public void methodName() throw IOException
D. public void methodName() throws IOException
E. public void methodName() throws Exception
答案: D、F

Question No: 8
8. Give the code fragment:
if(x>4){
System.out.println(“Test 1”);}
else if (x>9){
System.out.println(“Test 2”);}
else {
System.out.println(“Test 3”);}
Which range of value x would produce of output “Test 2”?
A. x<4
B. x>4
C. x>9
D. None
答案:D

Question No: 9
9. Give the following method:
public void example(){
try{
unsafe();
System.out.println(“Test1”);
}catch(SafeException e){System.out.println(“Test 2”);
}finally{System.out.println(“Test 3”);}
System.out.println(“Test 4”);
Which will display if method unsafe () run normally?
A. Test 1
B. Test 2
C. Test 3
D. Test 4

答案: A、C、D

Question No: 10
10. Which method you define as the starting point of new thread in a class from which new the thread can be excution?
A. public void start()
B. public void run()
C. public void int()
D. public static void main(String args[])
E. public void runnable()

答案:B

Question No: 11
11.Given the following class definition:
class A{
protected int i;
A(int i){
this.i=i;
}
}
which of the following would be a valid inner class for this class?
Select all valid answers:
A. class B{
}
B. class B extends A{
}
C. class B extends A{
B(){System.out.println(“i=”+i);}
}
D. class B{
class A{}
}
E. class A{}

答案:A

Question No: 12
12. Which modifier should be applied to a method for the lock of object this to be obtained prior to excution any of the method body?
A. synchronized
B. abstract
C. final
D. static
E. public

答案:A

Question No: 13
13. The following code is entire contents of a file called Example.java,causes precisely one error during compilation:
1) class SubClass extends BaseClass{
2} }
3) class BaseClass(){
4} String str;
5} public BaseClass(){
6} System.out.println(“ok”);}
7} public BaseClass(String s){
8} str=s;}}
9) public class Example{
10} public void method(){
11} SubClass s=new SubClass(“hello”);
12} BaseClass b=new BaseClass(“world”);
13} }
14} }
Which line would be cause the error?
A. 9 B. 10 C. 11 D.12

答案:C

Question No: 14
14. Which statement is correctly declare a variable a which is suitable for refering to an array of 50 string empty object?
A. String [] a
B. String a[]
C. char a[][]
D. String a[50]
F. Object a[50]

答案: A、B

Question No: 15
15. Give the following java source fragement:
//point x
public class Interesting{
//do something
}
Which statement is correctly Java syntax at point x?
A. import java.awt.*;
B.package mypackage
C. static int PI=3.14
D. public class MyClass{//do other thing…} E. class MyClass{//do something…}

答案: A、E

Question No: 16
16. Give this class outline:
class Example{
private int x;
//rest of class body…
}
Assuming that x invoked by the code java Example, which statement can made x be directly accessible in main() method of Example.java?
A. Change private int x to public int x
B. change private int x to static int x
C. Change private int x to protected int x
D. change private int x to final int x

答案:B

Question No: 17
17. the piece of preliminary analsis work describes a class that will be used frequently in many unrelated parts of a project
“The polygon object is a drawable, A polygon has vertex information stored in a vector, a color, length and width.”
Which Data type would be used?
A. Vector
B. int
C. String
D. Color
E. Date

答案: A、B、D

Question No: 18
18. A class design requires that a member variable should be accessible only by same package, which modifer word should be used?
A. protected
B. public
C. no modifer
D. private

答案:C

Question No: 19
19.Which declares for native method in a java class corrected?
A. public native void method(){}
B. public native void method();
C. public native method();
D. public void method(){native;}
E. public void native method();

答案:B

Question No: 20
20. Which modifer should be applied to a declaration of a class member variable for the value of variable to remain constant after the creation of the object?

答案: final

Question No: 21
21. Which is the main() method return of a application?
A. String
B. byte
C. char
D. void

答案:D

Question No: 22
22. Which is corrected argument of main() method of application?
A. String args
B. String ar[]
C. Char args[][]
D. StringBuffer arg[]

答案:B

Question No: 23
23. “The Employee object is a person, An Employee has appointment store in a vector, a hire date and a number of dependent”
short answer: use shortest statement declare a class of Employee.

答案: public class Employee extends Person

Question No: 24
24. Give the following class defination inseparate source files:
public class Example{
public Example(){//do something}
protected Example(int i){//do something}
protected void method(){//do something}
}
public class Hello extends Example{//member method and member variable}
Which methods are corrected added to the class Hello?
A. public void Example(){}
B. public void method(){}
C. protected void method(){}
D. private void method(){}

答案: A、B、C

Question No: 25
25. Float s=new Float(0.9F);
Float t=new Float(0.9F);
Double u=new Double(0.9);
Which expression?s result is true?
A. s==t
B. s.equals(t)
C. s==u
D. t.equals(u)

答案: A、B

Question No: 26
26. Give following class:
class AClass{
private long val;
public AClass(long v){val=v;}
public static void main(String args[]){
AClass x=new AClass(10L);
AClass y=new AClass(10L);
AClass z=y;
long a=10L;
int b=10;
}
}
Which expression result is true?
A. a==b;
B. a==x;
C. y==z;
D. x==y;
E. a==10.0;

答案: A、C、E

Question No: 27
27. A socket object has been created and connected to a standard internet service on a remote network server. Which construction give the most suitable means for reading ASCII data online at a time from the socket?
A. InputStream in=s.getInputStream();
B. DataInputStream in=new DataInputstream(s.getInputStream());
C. ByteArrayInputStream in=new ByteArrayInputStream(s.getInputStream());
D. BufferedReader in=new BufferedReader(new InputStreamReader(s.getInputStream()));
E. BufferedReader in=new BufferedReader(new InputStreamReader(s.getInputStream()),”8859-1”);

答案:E

Question No: 28
28. String s=”Example String”;
Which operation is legal?
A. s>>>=3;
B. int i=s.length();
C. s[3]=”x”;
D. String short_s=s.trim();
E. String t=”root”+s;

答案: B、D、E

Question No: 29
29. What happens when you try to compile and run the following program?
class Mystery{
String s;
public static void main(String[] args){
Mystery m=new Mystery();
m.go();
}
void Mystery(){
s=”constructor”;
}
void go(){
System.out.println(s);
}
}
A. this code will not compile
B. this code compliles but throws an exception at runtime
C. this code runs but nothing appears in the standard output
D. this code runs and “constructor” in the standard output
E. this code runs and writes ”null” in the standard output

答案:E

Question No: 30
30. What use to position a Button in a Frame ,only width of Button is affected by the Frame size, which Layout Button well be set ?
A. FlowLayout;
B. GridLayout;
C. North of BorderLayout
D. South of BorderLayout
E. East or West of BorderLayout

答案: C、D

Question No: 31
31. What use to position a Button in a Frame, size of Button is not affected by the Frame size, which Layout Button will be set?
A. FlowLayout;
B. GridLayout;
C. North of BorderLayout
D. South of BorderLayout
E. East or West of BorderLayout

答案:A

Question No: 32
32. An AWT GUI under exposure condition, which one or more method well be invoke when it redraw?
A. paint();
B. update();
C. repaint();
D. drawing();

答案:A

Question No: 33
33. Select valid identifier of Java:
A. userName
B. %passwd
C. 3d_game
D. $charge E. this

答案: A、D

Question No: 34
34. Which are Java keyword?
A. goto
B. null
C. FALSE
D. native
E. const

答案: A、B、D、E

Question No: 35
35. Run a corrected class: java ?Ccs AClass a b c <enter>
Which statement is true?
A. args[0]=”-cs”;
B. args[1]=”a b c”;
C. args[0]=”java”;
D. args[0]=”a”; E. args[1]=?b?

答案:D

Question No: 36
36. Give the following java class:
public class Example{
static int x[]=new int[15];
public static void main(String args[]){
System.out.println(x[5]);
}
}
Which statement is corrected?
A. When compile, some error will occur.
B. When run, some error will occur.
C. Output is zero.
D. Output is null.

答案:C

Question No: 37
37. Give the following java class:
public class Example{
public static void main(String args[]){
static int x[] = new int[15];
System.out.println(x[5]);
}
}
Which statement is corrected?
A. When compile, some error will occur.
B. When run, some error will occur.
C. Output is zero.
D. Output is null.

答案:A

Question No: 38
38. Short answer:
The decimal value of i is 12, the octal i value is:

答案: 014

Question No: 39
39. Short answer:
The decimal value of i is 7, the hexadecimal i value is:

答案: 0x7

Question No: 40
40. Which is the range of char?
A. 27~27-1
B. 0~216-1
C. 0~216
D. 0~28

答案:B

Question No: 41
41. Which is the range of int type?
A. -216~216-1
B.- 231~231-1
C. -232~232-1
D. -264~264-1

答案:B

Question No: 42
42. Give the following class:
public class Example{
String str=new String(“good”);
char ch[]={
public static void main(String args[]){
Example ex=new Example();
ex.change(ex.str,ex.ch);
System.out.println(ex.str+”and”+ex.ch);
}
public void change(String str,char ch[]){
str=”test ok”;ch[0]=?g?
}
}
Which is the output:
A. good and abc
B. good and gbc
C. test ok and abc
D. test ok and gbc

答案:B

Question No: 43
43. Which code fragments would correctly identify the number of arguments passed via command line to a Java application, exclude the name of the class that is being invoke.
A. int count = args.length;
B. int count = args.length-1;
C. int count=0; while(args[count]!=null)
count++;
D. int count=0;while
(!(args[count].equals(“”))) count++;

答案:A

Question No: 44
44. FilterOutputStream is the parent class for BufferedOutputStream, DataOutputStream and PrintStream. Which classes are valid argument for the constructor of a FilterOutputStream?
A. InputStream
B. OutputStream
C. File
D. RandomAccessFile
E. StreamTokenizer

答案:B

Question No: 45
45. Given a TextArea using a proportional pitch font and constructed like this:
TextArea t=new TextArea(“12345”,5,5);
Which statement is true?
A. The displayed width shows exactly five characters one each line unless otherwise constrained
B. The displayed height is five lines unless otherwise constrained
C. The maximum number of characters in a line will be five
D. The user will be able to edit the character string
E. The displayed string can use multiple fonts

答案:B

Question No: 46
46. Given a List using a proportional pitch font and constructed like this:
List l=new List(5,true);
Which statement is true?
A. The displayed item exactly five lines unless otherwise constrained
B. The displayed item is five lines init, but can displayed more than five Item by scroll
C. The maximum number of item in a list will be five.
D. The list is multiple mode

答案:B

Question No: 47
47. Given this skeleton of a class currently under construction:
public class Example{
int x,y,z;

public Example (int a, int b) {
//lots of complex computation
x=a; y=b;
}
public Example(int a, int b, int c){
// do everything the same as single argument
// version of constructor
// including assignment x=a, y=b, z=c
z=c;
}
}
What is the most concise way to code the “do everything…” part of the constructor taking two arguments?
Short answer:

答案: this(a,b);

Question No: 48
48. Which correctly create a two dimensional array of integers?
A. int a[][] = new int[][];
B. int a[10][10] = new int[][];
C. int a[][] = new int[10][10];
D. int [][]a = new int[10][10];
E. int []a[] = new int[10][10];

答案: C、D、E

Question No: 49
49. Which are correct class declarations? Assume in each case that the text constitutes the entire contents of a file called Fred.java?
A. public class Fred{
public int x = 0;
public Fred (int x){
this.x=x;
}
}
B. public class fred{
public int x = 0;
public Fred (int x){
this.x=x;
}
}
C. public class Fred extends MyBaseClass, MyOtherBaseClass{
public int x = 0;
public Fred(int xval){
x=xval;
}
}
D. protected class Fred{
private int x = 0;
private Fred (int xval){
x=xval;
}
}
E. import java.awt.*;
public class Fred extends Object{
int x;
private Fred(int xval){
x = xval;
}
}

答案: A、E

Question No: 50
50. A class design requires that a particular member variable must be accessible for direct access by any subclasses of this class. but otherwise not by classes which are not members of the same package. What should be done to achieve this?
A. The variable should be marked public
B. The variable should be marked private
C. The variable should be marked protected
D. The variable should have no special access modifier
E. The variable should be marked private and an accessor method provided

答案: C

Question No: 51
51．What might cause the current thread to stop executing?
A. An interrupted exception is thrown.
B. The thread execute a sleep() call.
C. The thread constructs a new thread
D. A thread of higher priority becomes ready
E. The thread executes a read() call on InputStream

答案: A、B、D、E

Question No: 52
52．Which statements are true about threads?
A. Threads created from the same class all finish together.
B. A thread can be created only by subclassing java.lang.Thread.
C. Invoking the suspend() method stops a thread so that it cannot be restarted.
D. The Java interpreter?s natural exit occurs when no non-daemon threads remain alive.
E. Uncoordinated changes to shared data by multiple threads may result in the data being read, or left, in an inconsistent state.

答案: D、E

Question No: 53
53．What might form part of a correct inner class declaration or combined declaration and instantiation?
A. private class C
B. new SimpleInterface(){
C. new ComplexInterface(x){
D. private final abstract class(
E. new ComplexClass() implements SimpleInterface

答案: A、B

Question No: 54
54． Which statements are true about the garbage collection mechanisms?
A. The garbage collection mechanism release memory at pridictable times.
B. A correct program must not depend upon the timing or order of garbage collection
C. Garbage collection ensures that a program will NOT run out of memory during execution
D. The programmer can indicate that a reference through a local variable is no longer going to be used.
E. The programmer has a mechanism that explicitly and immediately frees the memory used by Java objects.

答案: B、D

Question No: 55
55.Given the following,
4. String d = "bookkeeper";
5. d.substring(1,7);
6. d = "w" + d;
7. d.append("woo");
8. System.out.println(d);
what is the result?
A. wookkeewoo
B. wbookkeeper
C. wbookkeewoo
D. wbookkeeperwoo
E. Compilation fails.
F. An exception is thrown at runtime.

答案:E

Question No: 56
56. Which two statements are true about comparing two instances of the same class, given that the
equals() and hashCode() methods have been properly overridden? (Choose two.)
A. If the equals() method returns true, the hashCode() comparison == must
return true.
B. If the equals() method returns false, the hashCode() comparison != must return
true.
C. If the hashCode() comparison == returns true, the equals() method must return
true.
D. If the hashCode() comparison == returns true, the equals() method might
return true.
E. If the hashCode() comparison != returns true, the equals() method might
return true.

答案:A and D

Question No: 57
57. Given the following,
1. class X2 {
2. public X2 x;
3. public static void main(String [] args) {
4. X2 x2 = new X2();
5. X2 x3 = new X2();
6. x2.x = x3;
7. x3.x = x2;
8. x2 = new X2();
9. x3 = x2;
10. doComplexStuff();
11. }
12. }
after line 9 runs, how many objects are eligible for garbage collection?
A. 0
B. 1
C. 2
D. 3
E. 4

答案:C

Question No: 58
58. Which two are true about a method-local inner class?
A. It must be marked final.
B. It can be marked abstract.
C. It can be marked public.
D. It can be marked static.
E. It can access private members of the enclosing class.

答案:A E

Question No: 59
59. Given the following,
1.public class TestObj {
2. public static void main (String [] args) {
3. Object o = new Object() {
4. public boolean equals(Object obj) {
5. return true;
6. }
7. }
8. System.out.println(o.equals("Fred"));
9. }
10.}
what is the result?
A. An exception occurs at runtime.
B. true
C. fred
D. Compilation fails because of an error on line 3.
E. Compilation fails because of an error on line 4.
F. Compilation fails because of an error on line 8.
G. Compilation fails because of an error on a line other than 3, 4, or 8.

答案:G

Question No: 60
60. Given the following,
1. class Test {
2.
3. public static void main(String [] args) {
4. printAll(args);
5. }
6.
7. public static void printAll(String[] lines) {
8. for(int i=0;i<lines.length;i++){
9. System.out.println(lines[i]);
10. Thread.currentThread().sleep(1000);
11. }
12. }
13. }
the static method Thread.currentThread() returns a reference to the currently executing
Thread object. What is the result of this code?
A. Each String in the array lines will output, with a 1-second pause.
B. Each String in the array lines will output, with no pause in between because this method is
not executed in a Thread.
C. Each String in the array lines will output, and there is no guarantee there will be a pause
because currentThread() may not retrieve this thread.
D. This code will not compile.

答案:D

Question No: 61
61. Which two are true?
A. The notifyAll() method must be called from a synchronized context.
B. To call wait(), an object must own the lock on the thread.
C. The notify() method is defined in class java.lang.Thread.
D. When a thread is waiting as a result of wait(), it release its locks.
E. The notify() method causes a thread to immediately release its locks.
F. The difference between notify() and notifyAll() is that notifyAll() notifies
all waiting threads, regardless of the object they’re waiting on.

答案:A D

例题1：
Choose the three valid identifiers from those listed below.
A. IDoLikeTheLongNameClass
B. $byte
C. const
D. _ok
E. 3_case
解答：A, B, D
　　点评：Java中的标示符必须是字母、美元符($)或下划线(_)开头。关键字与
保留字不能作为标示符。选项C中的const是Java的保留字，所以不能作标示符。
选项E中的3_case以数字开头，违反了Java的规则。
例题2：
How can you force garbage collection of an object?
A. Garbage collection cannot be forced
B. Call System.gc().
C. Call System.gc(), passing in a reference to the object to be
garbage collected.
D. Call Runtime.gc().
E. Set all references to the object to new values（null, for
example）.
解答：A
　　点评：在Java中垃圾收集是不能被强迫立即执行的。调用System.gc()或
Runtime.gc()静态方法不能保证垃圾收集器的立即执行，因为，也许存在着更高
优先级的线程。所以选项B、D不正确。选项C的错误在于，System.gc()方法是不
接受参数的。选项E中的方法可以使对象在下次垃圾收集器运行时被收集。
例题3：
Consider the following class:
1. class Test(int i) {
2. void test(int i) {
3. System.out.println("I am an int.");
4. }
5. void test(String s) {
6. System.out.println("I am a string.");
7. }
8.
9. public static void main(String args[]) {
10. Test t=new Test();
11. char ch="y";
12. t.test(ch);
13. }
14. }
Which of the statements below is true?(Choose one.)
A. Line 5 will not compile, because void methods cannot be
overridden.
B. Line 12 will not compile, because there is no version of test()
that rakes a char argument.
C. The code will compile but will throw an exception at line 12.
D. The code will compile and produce the following output: I am an
int.
E. The code will compile and produce the following output: I am a
String.
解答：D
　　点评：在第12行，16位长的char型变量ch在编译时会自动转化为一个32位长
的int型，并在运行时传给void test(int i)方法。
例题4：
Which of the following lines of code will compile without error？
A.
int i=0;
if (i) {
System.out.println("Hi");
}
B.
boolean b=true;
boolean b2=true;
if(b==b2) {
System.out.println("So true");
}
C.
int i=1;
int j=2;
if(i==1|| j==2)
System.out.println("OK");
D.
int i=1;
int j=2;
if (i==1 &| j==2)
System.out.println("OK");
解答：B, C
点评：选项A错，因为if语句后需要一个boolean类型的表达式。逻辑操作有^、
&、| 和 &&、||,但是"&|"是非法的，所以选项D不正确。
例题5：
Which two demonstrate a "has a" relationship? (Choose two)
A. public interface Person { }
public class Employee extends Person{ }
B. public interface Shape { }
public interface Rectandle extends Shape { }
C. public interface Colorable { }
public class Shape implements Colorable
{ }
D. public class Species{ }
public class Animal{private Species species;}
E. interface Component{ }
class Container implements Component{
private Component[] children;
}
解答：D, E
　　点评：在Java中代码重用有两种可能的方式，即组合（"has a"关系）和
继承（"is a"关系）。"has a"关系是通过定义类的属性的方式实现的；而
"is a"关系是通过类继承实现的。本例中选项A、B、C体现了"is a"关系；
选项D、E体现了"has a"关系。

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例题6：
Which two statements are true for the class java.util.TreeSet?
(Choose two)
A. The elements in the collection are ordered.
B. The collection is guaranteed to be immutable.
C. The elements in the collection are guaranteed to be unique.
D. The elements in the collection are accessed using a unique key.
E. The elements in the collection are guaranteed to be synchronized
解答：A, C
　　点评：TreeSet类实现了Set接口。Set的特点是其中的元素惟一，选项C正
确。由于采用了树形存储方式，将元素有序地组织起来，所以选项A也正确。
例题7：
True or False: Readers have methods that can read and return floats
and doubles.
A. Ture
B. False
解答：B
　　点评： Reader/Writer只处理Unicode字符的输入输出。float和double可以
通过stream进行I/O.
例题8：
What does the following paint() method draw?
1. public void paint(Graphics g) {
2. g.drawString("Any question", 10, 0);
3. }
A. The string "Any question?", with its top-left corner at 10,0
B. A little squiggle coming down from the top of the component.
解答：B
　　点评：drawString(String str, int x, int y)方法是使用当前的颜色和字
符，将str的内容显示出来，并且最左的字符的基线从（x,y）开始。在本题中，
y=0，所以基线位于最顶端。我们只能看到下行字母的一部分，即字母'y'、
'q'的下半部分。
例题9：
What happens when you try to compile and run the following
application? Choose all correct options.
1. public class Z {
2. public static void main(String[] args) {
3. new Z();
4. }
5.
6. Z() {
7. Z alias1 = this;
8. Z alias2 = this;
9. synchronized(alias1) {
10. try {
11. alias2.wait();
12. System.out.println("DONE WAITING");
13. }
14. catch (InterruptedException e) {
15. System.out.println("INTERR
UPTED");
16. }
17. catch (Exception e) {
18. System.out.println("OTHER EXCEPTION");
19. }
20. finally {
21. System.out.println
("FINALLY");
22. }
23. }
24. System.out.println("ALL DONE");
25. }
26. }
A. The application compiles but doesn''t print anything.
B. The application compiles and print "DONE WAITING"
C. The application compiles and print "FINALLY"
D. The application compiles and print "ALL DONE"
E. The application compiles and print "INTERRUPTED"
解答：A
　　点评：在Java中，每一个对象都有锁。任何时候，该锁都至多由一个线程控
制。由于alias1与alias2指向同一对象Z，在执行第11行前，线程拥有对象Z的
锁。在执行完第11行以后，该线程释放了对象Z的锁，进入等待池。但此后没有
线程调用对象Z的notify()和notifyAll()方法，所以该进程一直处于等待状态，
没有输出。
例题10：
Which statement or statements are true about the code listed below?
Choose three.
1. public class MyTextArea extends TextArea {
2. public MyTextArea(int nrows, int ncols) {
3. enableEvents(AWTEvent.TEXT_
EVENT_MASK);
4. }
5.
6. public void processTextEvent
(TextEvent te) {
7. System.out.println("Processing a text event.");
8. }
9. }
A. The http://www.qd.sd.cn code must appear in a file called MyTextArea.java
B. Between lines 2 and 3, a call should be made to super(nrows,
ncols) so that the new component will have the correct size.
C. At line 6, the return type of processTextEvent() should be
declared boolean, not void.
D. Between lines 7 and 8, the following code should appear: return
true.
E. Between lines 7 and 8, the following code should appear:
super.processTextEvent(te).
解答：A, B, E
　　点评：由于类是public，所以文件名必须与之对应，选项A正确。如果不在
2、3行之间加上super(nrows,ncols)的话，则会调用无参数构建器TextArea(),
使nrows、ncols信息丢失，故选项B正确。在Java2中，所有的事件处理方法都不
返回值，选项C、D错误。选项E正确，因为如果不加super.processTextEvent
(te)，注册的listener将不会被唤醒。

posted on 2006-02-15 17:50 bluesky 阅读(5276) 评论(0) 编辑收藏所属分类: 记事本

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