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Brian同步规则:如果你正在写一个变量,它可能在接下来被另一个线程读取,或者正在读取一个上一次已经被一个线程写过的变量,那么你就必须使用同步,并且,读写线程都必须使用相同的监视器锁同步
public class Test implements Runnable {
public int flag = 1;
static Object o1 = new Object(), o2 = new Object();
public void run() {
System.out.println("flag=" + flag);
if(flag == 1) {
synchronized(o1) {
try {
Thread.sleep(500);
} catch (Exception e) {
e.printStackTrace();
}
synchronized(o2) {
System.out.println("1");
}
}
}
if(flag == 0) {
synchronized(o2) {
try {
Thread.sleep(500);
} catch (Exception e) {
e.printStackTrace();
}
synchronized(o1) {
System.out.println("0");
}
}
}
}
public static void main(String[] args) {
Test td1 = new Test();
Test td2 = new Test();
td1.flag = 1;
td2.flag = 0;
Thread t1 = new Thread(td1);
Thread t2 = new Thread(td2);
t1.start();
t2.start();
}
}
public class TestUnsafeThread extends Thread{
static int allval=49;
//
public void run() {
allval++;
try {
Thread.sleep(0);
System.out.println("allval 的值为:"+allval);
}
catch (InterruptedException ie) {
ie.printStackTrace();
}
}
public static void main(String[] args) {
Thread t1=new Thread (new TestUnsafeThread());
Thread t2=new Thread (new TestUnsafeThread());
t1.start();
t2.start();
}
}