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天快黑了 — Wed, 04 Aug 2010 09:40:00 GMT

大家不用兛_��E�序实际逻辑是否正确�Q�只是好奇，��Z��么这个程序会hang住不�q�行了？而且CPU会占�?00%

import java.util.HashMap;

public class TestLock {

private HashMap map = new HashMap();

public TestLock() {
Thread t1 = new Thread() {
public void run() {
for(int i=0; i<50000; i++) {
map.put(new Integer(i), i);
}
System.out.println("t1 over");
}
};

Thread t2 = new Thread() {
public void run() {
for(int i=0; i<50000; i++) {
map.put(new Integer(i), i);
}

System.out.println("t2 over");
}
};

t1.start();
t2.start();

}

public static void main(String[] args) {
new TestLock();
}
}

Dump thread会看刎ͼ��E�序hang刎ͼ�

"Thread-1" prio=6 tid=0x00c70bd8 nid=0x914 runnable [0x02ebf000..0x02ebfc68]
at java.util.HashMap.put(HashMap.java:420)
at TestLock$2.run(TestLock.java:20)

"Thread-0" prio=6 tid=0x00c70a50 nid=0x578 runnable [0x02e7f000..0x02e7fb68]
at java.util.HashMap.put(HashMap.java:420)
at TestLock$1.run(TestLock.java:11)

天快黑了 2010-08-04 17:40 发表评论

另类NoClassDefFoundError

天快黑了 — Thu, 29 Jul 2010 07:54:00 GMT

通常NoClassDefFoundError产生的原因都是由于用到的class在CLASSPATH中找不到�?br />
�q�有下面一�U�另�cȝ��NoClassDefFoundError�Q?br /> 1. Class A 调用 Class B
2. JVM��试加蝲Class B�Q��ƈ执行Class B的静态块
3. Class B的静态块内抛出RuntimeException�Q�从而导致JVM加蝲Class B��p�|
4. 之后�Q��Q何类只要调用Class B�Q�就会出现NoClassDefFoundError

大家可以�q�行下面的例子试一�?

1 public class B
2 {
3     static {
4         String s = null;
5         s.substring(0);
6     }
7 }

1 public class A
2 {
3     public static void main(String[] args)
4     {
5         try
6         {
7             B b = new B();
8         }
9         catch (Throwable e)
10         {
11             e.printStackTrace();
12         }
13
14         try
15         {
16             B b = new B();
17         }
18         catch (Throwable e)
19         {
20             e.printStackTrace();
21         }
22     }
23 }

天快黑了 2010-07-29 15:54 发表评论