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我运行的结果是
Thread-1: try get lock A...
Thread-1: lock A got.
Thread-2: try get lock A...
Thread-1: try get lock B...
Thread-1: lock B got.
Thread-1: lock B released.
Thread-2: lock A got.
Thread-1: lock A released.
Thread-2: try get lock B...
Thread-2: lock B got.
Thread-2: lock B released.
Thread-2: lock A released.
其中对
Thread-2: lock A got.
Thread-1: lock A released.
两行有点疑惑，乍一看好像Thread-2在Thread-1释放lock A前就已经获取了lock A，但其实在执行
System.out.println("Thread-1: lock A released.");
这句前Thread-1就已经释放了lock A，只是之后CPU先执行了Thread-2的
System.out.println("Thread-2: lock A got.");
Thread-2随即被sleep，CPU再去执行"Thread-1: lock A released."那句，可否这样理解？
因该是的吧，线程1在获取锁A后，在
synchronized (Main.LOCK_A) {
System.out.println("Thread-1: lock A got.");
Main.sleep1s();
System.out.println("Thread-1: try get lock B...");
synchronized (Main.LOCK_B) {
System.out.println("Thread-1: lock B got.");
Main.sleep1s();
}
System.out.println("Thread-1: lock B released.");
}
结尾就已经释放，所以线程2获取锁A和
System.out.println("Thread-1: lock A released.");
的先后顺序并不确定
- 1
狠美味2013
package com.itranswarp.world;
/**
* 测试专用
*
* @author hadoop
*
*/
public class Main {
static final Object LOCK_A = new Object();
static final Object LOCK_B = new Object();
public static void main(String[] args) {
new Thread1().start();
new Thread2().start();
}
static void sleep1s() {
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
class Thread1 extends Thread {
public void run() {
System.out.println("Thread-1: try get lock A...");
synchronized (Main.LOCK_A) {
System.out.println("Thread-1: lock A got.");
Main.sleep1s();
System.out.println("Thread-1: try get lock B...");
synchronized (Main.LOCK_B) {
System.out.println("Thread-1: lock B got.");
Main.sleep1s();
}
System.out.println("Thread-1: lock B released.");
}
System.out.println("Thread-1: lock A released.");
}
}
class Thread2 extends Thread {
public void run() {
System.out.println("Thread-2: try get lock A...");
synchronized (Main.LOCK_A) {
System.out.println("Thread-2: lock A got.");
Main.sleep1s();
System.out.println("Thread-2: try get lock B...");
synchronized (Main.LOCK_B) {
System.out.println("Thread-2: lock B got.");
Main.sleep1s();
}
System.out.println("Thread-2: lock B released.");
}
System.out.println("Thread-2: lock A released.");
}
}