2010年10月25日随笔档案 - Sun River

2010年10月25日

Java Faqs 2

Question How do you delete a Cookie within a JSP? (JSP)

Answer

Cookie mycook = new Cookie("name","value");

response.addCookie(mycook);

Cookie killmycook = new Cookie("mycook","value");

killmycook.setMaxAge(0);

killmycook.setPath("/");

killmycook.addCookie(killmycook);

Question How many types of protocol implementations does RMI have? (RMI)

Answer RMI has at least three protocol implementations: Java

Remote Method Protocol(JRMP), Internet Inter ORB Protocol(IIOP),

and Jini Extensible Remote Invocation(JERI). These are alternatives,

not part of the same thing, All three are indeed layer 6 protocols for

those who are still speaking OSI reference model.

Question What are the different identifier states of a Thread?

(Core Java)

Answer The different identifiers of a Thread are:

R - Running or runnable thread

S - Suspended thread

CW - Thread waiting on a condition variable

MW - Thread waiting on a monitor lock

MS - Thread suspended waiting on a monitor lock

Question What is the fastest type of JDBC driver? (JDBC)

Answer JDBC driver performance will depend on a number of

issues:

(a) the quality of the driver code,

(b) the size of the driver code,

(d) network topology,

(e) the number of times your request is translated to a different API.

In general, all things being equal, you can assume that the more your

request and response change hands, the slower it will be. This

means that Type 1 and Type 3 drivers will be slower than Type 2

drivers (the database calls are make at least three translations versus

two), and Type 4 drivers are the fastest (only one translation).

Question Request parameter How to find whether a parameter

exists in the request object? (Servlets)

Answer 1.boolean hasFoo = !(request.getParameter("foo") ==

null || request.getParameter("foo").equals(""));

2. boolean hasParameter =

request.getParameterMap().contains(theParameter);

(which works in Servlet 2.3+)

Question How can I send user authentication information while

makingURLConnection? (Servlets)

Answer You’ll want to use

HttpURLConnection.setRequestProperty and set all the appropriate

headers to HTTP authorization.

Question How do I convert a numeric IP address like 192.18.97.39

into a hostname like java.sun.com? (Networking)

Answer

Question How many methods do u implement if implement the

Serializable Interface? (Core Java)

Answer The Serializable interface is just a "marker" interface,

with no methods of its own to implement. Other ’marker’ interfaces

are

java.rmi.Remote

java.util.EventListener

String hostname =InetAddress.getByName("192.18.97.39").getHostName();

posted @ 2010-10-25 17:08 Sun River| 编辑收藏

Java Faqs 1

Question What is the query used to display all tables names in

SQL Server (Query analyzer)? (JDBC)

Answer select * from information_schema.tables

Question What is Externalizable? (Core Java)

Answer Externalizable is an Interface that extends Serializable

Interface. And sends data into Streams in Compressed Format. It has

two methods, writeExternal(ObjectOuput out) and

readExternal(ObjectInput in).

Question What modifiers are allowed for methods in an Interface?

Answer Only public and abstract modifiers are allowed for

methods in interfaces.

Question How many types of JDBC Drivers are present and what

are they? (JDBC)

Answer There are 4 types of JDBC Drivers

Type 1: JDBC-ODBC Bridge Driver

Type 2: Native API Partly Java Driver

Type 3: Network protocol Driver

Type 4: JDBC Net pure Java Driver

Question What is the difference between ServletContext and

PageContext? (JSP)

Answer ServletContext: Gives the information about the container

PageContext: Gives the information about the Request.

Question How to pass information from JSP to included JSP?

Answer Using <%jsp:param> tag.

posted @ 2010-10-25 16:07 Sun River| 编辑收藏

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