关于Java中synchronized关键字的案例

synchronize同步问题对于锁得理解

package test.synchronize;

public class AmSynchornizeClass {
	private int index=0;
	
	private static int staticIndex = 0;
	
	//成员锁对象
	private Object lock = new Object();
	
	
	/**
	 * 锁对象是this
	 * @return
	 */
	public synchronized int getIndex() {
		return index;	
	}
	
	/**
	 * 锁对象this 等同于  public synchronized int getIndex(){...}
	 */
	public int getIndex2() {
		synchronized (this) {
			return index;	
		}
	}
	
	/**
	 * 锁对象时成员变量lock
	 * @return
	 */
	public int getIndex3() {
		synchronized (lock) {
			return index;	
		}
	}
	
	/**
	 * 错误案例:锁对象new Object()离开了方法getIndex4()块没有实际意义
	 * @return
	 */
	public int getIndex4(){
		synchronized(new Object()){
			return index;	
		}
	}
	
	public synchronized void increaseIndex() {
		try {
			Thread.sleep(5*1000);
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
		index++;
	}
	
	public void increaseIndex2() {
		synchronized(this){
			try {
				Thread.sleep(5*1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
		    index++;
		}
	}
	
	public void increaseIndex3() {
		synchronized(lock){
			try {
				Thread.sleep(5*1000);
			} catch (InterruptedException e) {
				e.printStackTrace();
			}
			 index++;
		}
	}
	
	/**
	 * 锁对象是AmSynchornizeClass.class等同于public  static void substract2()
	 */
	public synchronized static void substract(){
		staticIndex--;
	}
	
	public static void substract2(){
		synchronized(AmSynchornizeClass.class){
			staticIndex--;
		}
	}
}

package test.synchronize;

import org.junit.Test;

public class TestSynchronize {
	@Test
	public void testSynchronizedLock1() {
		final AmSynchornizeClass asc1 = new AmSynchornizeClass();
		final AmSynchornizeClass asc2 = new AmSynchornizeClass();
		Runnable getThread = new Runnable(){
			@Override
			public void run() {
				System.out.println("go into get method()...");
				System.out.println(asc1.getIndex());
				System.out.println("get out from get method()...");
			}
		};
		
		Runnable increaseThread = new Runnable(){
			@Override
			public void run() {
				System.out.println("go into increase method()...");
				asc2.increaseIndex();
				System.out.println("go out increase method()...");
			}
		};
		
		Thread t1= new Thread(increaseThread);
		Thread t2= new Thread(getThread);
		
		t1.start();
		t2.start();
		try {
			while(true){
				if(t1.isAlive() || t2.isAlive()){
						Thread.sleep(200);
				} else {
					break;
				}
			}
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
	
	@Test
	public void testSynchronizeLock() {
		final AmSynchornizeClass asc = new AmSynchornizeClass();
		Runnable getThread = new Runnable(){
			@Override
			public void run() {
				System.out.println("go into get method()...");
				System.out.println(asc.getIndex());
				System.out.println("get out from get method()...");
			}
		};
		
		Runnable increaseThread = new Runnable(){
			@Override
			public void run() {
				System.out.println("go into increase method()...");
				asc.increaseIndex();
				System.out.println("go out increase method()...");
			}
		};
		
		Thread t1= new Thread(increaseThread);
		Thread t2= new Thread(getThread);
		
		t1.start();
		t2.start();
		try {
			while(true){
				if(t1.isAlive() || t2.isAlive()){
						Thread.sleep(200);
				} else {
					break;
				}
			}
		} catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
}