Sun LiWei

CheckStyle only audits your code instead of formatting code. It's better than nothing. I use Eclipse all the time and the built-in formatter of Eclipse is not good enough for SCJD, I think.

I found that Check Style 4.0.91(checkstyle.sf.net )has a built-in configuration "SUN Checks" , Does anyone know whether it suitable for SCJD???

So,is the initiating order of a inner class is

1)super()
3)the hidden reference to the outter class(maybe here)
2)instance variable(s)
3)the hidden reference to the outter class(also maybe here)
4)it's own constructor

This hidden reference is the thing i don't know before.when exactly this reference is initialized?

class Outer { private String foo = "Outer.foo"; private String bar = "Outer.bar"; private Inner1 inner1 = new Inner1(); private Inner2 inner2 = new Inner2(); private class Inner1 { private String bar = "Inner1.bar"; Inner1() { System.out.println("new " + getClass().getName() + ": "); System.out.println(" foo=" + getFoo()); System.out.println(" bar=" + getBar()); } String getFoo() { return foo; } String getBar() { return bar; } } private class Inner2 extends Inner1 { private String foo = "Inner2.foo"; Inner2() { } String getFoo() { return foo; } String getBar() { return bar; } } public static void main(String[] args) { new Outer(); } }

Output:
new Outer$Inner1:
foo=Outer.foo
bar=Inner1.bar
new Outer$Inner2:
foo=null
java.lang.NullPointerException
at Outer.access$100(JavaTest.java:1)
at Outer$Inner2.getBar(JavaTest.java:37)
at Outer$Inner1.<init>(JavaTest.java:14)
at Outer$Inner2.<init>(JavaTest.java:29)
at Outer.<init>(JavaTest.java:6)
at Outer.main(JavaTest.java:43)


I can't explain the null situation here.


why NullPointerExceptin is thrown??? why foo is null in Inner2 class?what is the initiating order of a java class ??

I have a thread which using DatagramSocket in the run() method:
MyThread extends Thread{
public void run(){
try{
DatagramSocket socket=new DatagramSocket();
socket.send(...);
socket.recieve(...);
socket.close();
}catch(Exception e){
e.printStackTrace();
}
}
}
When I generate tens of threads with MyThread, most of the threads run without exception,but there're always some threads throw a SocketTimeoutException,the network is ok though,when i run one thread a time,no exception! I can't figure it out.Help me.

Maybe the following will make my quesion clear
two pc-servers,both have 1 GB memory and one P4 CPU,one is Linux and the other is Solaris 8(x86 version),both installed with resin 2.x and JDK 1.4.2, which one is more stable and faster when run a web application on resin?
[ July 17, 2003: Message edited by: Sun LiWei ]

Generally speaking,There's JDK on Linux,Windows And Solaris. And I wondered which is the best platform for JDK.It's seems that hotspot JVM can run better on Solaris than other two.But I am not sure of that

Did anyone know the performance of JDK 1.4.x on different operation systems,like Solaris,Linux,FreeBSD and Windows? It seems the muti-threads performance on Solaris is better than other systems?Is that right??

o ne of the policy of general database connection pool is creating new connection for every thread who request database connection by calling getConnection() method(normally,this method is synchronized.I wondered is there any synchronization problem if give the same connection object to mutiple threads.On the other words,is it safe if two thread use the same connection object concurrency?
[ June 16, 2003: Message edited by: Sun LiWei ]

in jdk 1.4,the isClosed() and isConnected() methods of Sokcet class does't detect whether the tcp connection is closed by remote host.
Only if the client socket invoke the s.close(),the two methods will show right result. It seems there's no way to know whether the tcp connection is closed by remote host.

There is a class ThreadLocal in jdk 1.2,I am still not understand this class after I read the jdk documents.It's maybe a silly question,but I am sucked.
class T extends Thread { public int k; }
in class T,the variable k is thread local variables,right?? every instance of T have its own copy of k.Did

sin(Math.PI/2) does not mean sin(90).
PI/2 != 90

class AnonyClass { AnonyClass getAnonyClass() throws Exception { return new AnonyClass () { { String s = "Hello"; if (s.equals("Hello")) { throw new Exception(); } } }; } }
it compiles in
java version "1.4.1_01"
Java(TM) 2 Runtime Environment, Standard Edition (build 1.4.1_01-b01)
Java HotSpot(TM) Client VM (build 1.4.1_01-b01, mixed mode)
[ October 28, 2002: Message edited by: Sun LiWei ]

No need for the answer now,I am using log4j now,it's powerful and easier to use

I found that the same logger only update logging message to the log file when using FileHandler.How can I make it append message into the file.For example:
class Test { private Logger logger = Logger.getLogger(this.getClass().getName()); public Test () { logger.log(Level.SEVERE, "This is a severe level message!"); } public void testLog() { logger.info("Message sent from method call."); } public static void main(String[] args){ Logger logger = Logger.getLogger("main()"); try { LogManager.getLogManager().readConfiguration(new FileInputStream("logging.properties")); } catch(IOException ioe) { logger.log(Level.SEVERE, "Unable to read Configuration", ioe); } Test example = new Test(); example.testLog(); Test2 t=new Test2(); t.testLog(System.currentTimeMillis()); } }
no matter how many times when I execute the code,the logger with the same name only update the log file.How can I change the logger's behavior from update to append??