java的ThreadLocal类的用法，ThreadLocal是一个支持泛型的类，用在多线程中用于防止并发冲突问题。

例如下面的一个例子，就是用于线程增加1，但是相互不冲突

package com.test.threadlocal;

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

class Local
{
	private static ThreadLocal<Integer> num=new ThreadLocal<Integer>()
			{
				protected synchronized Integer initialValue()
				{
					return 1;
				}
			};
			
	public static void add()
	{
		num.set(num.get()+1);
	}
	public static int get()
	{
		return num.get();
	}
}

class SelfThread extends Thread
{
	public void run()
	{
		for(int i=0;i<1000;i++)
		{
			System.out.println(this.getName()+"  "+Local.get());
			this.yield();
			Local.add();
		}
	}
}
public class MyThreadLocal {

	/**
	 * @param args
	 */
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		ExecutorService exec=Executors.newCachedThreadPool();
		for(int i=0;i<5;i++)
		{
			exec.execute(new SelfThread());
		}
		
		exec.shutdown();
	}

}

输出结果

Thread-3  973
Thread-1  808
Thread-3  974
Thread-1  809
Thread-3  975
Thread-1  810
Thread-3  976
Thread-1  811
Thread-3  977
Thread-1  812
Thread-3  978
Thread-1  813
Thread-3  979
Thread-1  814
Thread-3  980
Thread-1  815
Thread-3  981
Thread-1  816
Thread-3  982
Thread-1  817
Thread-3  983
Thread-1  818
Thread-3  984
Thread-1  819
Thread-3  985
Thread-1  820
Thread-3  986
Thread-1  821
Thread-3  987
Thread-1  822
Thread-3  988
Thread-1  823
Thread-3  989
Thread-1  824
Thread-3  990
Thread-1  825
Thread-3  991
Thread-1  826
Thread-3  992
Thread-1  827
Thread-3  993
Thread-1  828
Thread-3  994
Thread-1  829
Thread-3  995
Thread-1  830
Thread-3  996
Thread-1  831
Thread-3  997
Thread-1  832
Thread-3  998
Thread-1  833
Thread-3  999
Thread-1  834
Thread-3  1000
Thread-1  835
Thread-1  836
Thread-1  837
Thread-1  838
Thread-1  839
Thread-1  840
Thread-1  841
Thread-1  842
Thread-1  843
Thread-1  844
Thread-1  845
Thread-1  846
Thread-1  847
Thread-1  848
Thread-1  849
Thread-1  850
Thread-1  851
Thread-1  852
Thread-1  853
Thread-1  854
Thread-1  855
Thread-1  856
Thread-1  857
Thread-1  858
Thread-1  859
Thread-1  860
Thread-1  861
Thread-1  862
Thread-1  863
Thread-1  864
Thread-1  865
Thread-1  866
Thread-1  867
Thread-1  868
Thread-1  869
Thread-1  870
Thread-1  871
Thread-1  872
Thread-1  873
Thread-1  874

我们发现，线程会相互切换，但是每个线程都保持了增加1的顺序，说明没有线程之间的相互干扰。

java的ThreadLocal类的用法