java 集合类的排序主要是用Collections.sort方法,Collections和Collection是不一样的,前者是类,后者是接口,在这里,我主要是想说明它的sort方法的几种类型,
提示：实现接口的方法时，只需要比较两个数，大的返回1，相等返回0，小于返回-1。简单的说就是在方法里这样写：num>s.num?1:(num==s.num?0:-1); num是被比较的数，s.num是比较的数，
1.Collection.sort(List arg0);
这种是最简单的一种排序方法，只需要实现他的Comparable 接口及实现public int compareTo(Object arg0)方法即可。
2.Collection.srot(List arg0,Comparator arg1);
这种加入了比较器，具有更大的灵活性，便于管理，比较器可作为内部静态类的，以便于管理。比较器必须实现Comparator接口，具体可参照下列代码：
package com.gc.list;
import java.util.*;
public class ArrayListTest {
public static void printElements(Collection c){
Iterator it=c.iterator();
while(it.hasNext()){
System.out.println(it.next());
}
}
public static void main(String[] args){
ArrayList a1=new ArrayList();
/*
a1.add("zhangsan");
a1.add("lisi");
a1.add("wangwu");
*/
/*
a1.add(new Point(1,1));
a1.add(new Point(2,2));
a1.add(new Point(3,3));
for(int i=0;i<a1.size();i++){
System.out.println(a1.get(i));
}
Object[] objs=a1.toArray();
for(int i=0;i<objs.length;i++){
System.out.println(objs[i]);
}
List l=Arrays.asList(objs);
System.out.println(l);*/
//l.add("chuyang");
//l.set(0,new Point(4,4));
/*
Iterator it=a1.iterator();
while(it.hasNext()){
System.out.println(it.next());
}
*/
Student s1=new Student(4,"zhangsan");
Student s2=new Student(2,"lisi");
Student s3=new Student(3,"wangwu");
Student s4=new Student(4,"mybole");
a1.add(s1);
a1.add(s2);
a1.add(s3);
a1.add(s4);
//Collections.sort(a1);
Collections.sort(a1,new Student.StudentComparator());
printElements(a1);
System.out.println(Collections.max(a1));
}
}
class Point{
int x, y;
Point(int x,int y){
this.x=x;
this.y=y;
}
public String toString(){
return ("x="+x+","+"y="+y);
}
}
class Student implements Comparable{
int num;
String name;
Student(int num,String name){
this.num=num;
this.name=name;
}
static class StudentComparator implements Comparator{
public int compare(Object o1,Object o2){
Student s1=(Student) o1;
Student s2=(Student) o2;
int result=s1.num>s2.num?1:(s1.num==s2.num?0:-1);
if (result==0){
result=s1.name.compareTo(s2.name);
}
return result;
}
}
public int compareTo(Object arg0) {
Student s=(Student) arg0;
return num>s.num?1:(num==s.num?0:-1);
}
public String toString(){
return "num:"+num+","+"name:"+name;
}
}