One of the difference between JDK1.6.0 and JDK1.7.0

1. The test java code:

package com.haowei.oom;

import com.haowei.Util;

import java.util.ArrayList;

public class OOM {

    public static void stringInternOOM(){

        int counter = 1;

        try{

            int max = Integer.MAX_VALUE;

            ArrayList list = new ArrayList();

            for(int i=0;i<max;i++){

                String str = String.valueOf(i);

                list.add(str.intern());

                counter++;

            }

        }catch(Exception e){

            e.printStackTrace();

        }finally{

            Util.log("the max String.Intern counter = " + counter);

        }

    }

    

    public static void main(String args[]){

        stringInternOOM();

    }

}

2. The execute script:

java -cp . -Xms16m -Xmx16m -XX:PermSize=16m -XX:MaxPermSize=16m com/haowei/oom/OOM

3. The result of JDK1.6.0

*********version begin****************

Apache Ant(TM) version 1.8.2 compiled on December 20 2010

java version "1.6.0_26"

Java(TM) SE Runtime Environment (build 1.6.0_26-b03)

Java HotSpot(TM) Client VM (build 20.1-b02, mixed mode, sharing)

*********version end****************



*************** begin to run java ***************



the max String.Intern counter = 348980

Exception in thread "main" java.lang.OutOfMemoryError: PermGen space

	at java.lang.String.intern(Native Method)

	at com.haowei.oom.OOM.stringInternOOM(Unknown Source)

	at com.haowei.oom.OOM.main(Unknown Source)

 4.The result of JDK1.7.0

*********version begin****************

Apache Ant(TM) version 1.8.2 compiled on December 20 2010

openjdk version "1.7.0-internal-debug"

OpenJDK Runtime Environment (build 1.7.0-internal-debug-haowei_2012_02_06_22_42-b00)

OpenJDK Client VM (build 21.0-b17-jvmg, mixed mode)

*********version end****************



*************** begin to run java ***************



the max String.Intern counter = 304460

Exception in thread "main" java.lang.OutOfMemoryError: Java heap space

	at java.lang.Integer.toString(Integer.java:333)

	at java.lang.String.valueOf(String.java:3007)

	at com.haowei.oom.OOM.stringInternOOM(Unknown Source)

	at com.haowei.oom.OOM.main(Unknown Source)

VM option 'PermSize=16m'

VM option 'MaxPermSize=16m'