了解同步
给出这段代码：
public class Messager implements Runnable {
public static void main(String[] args) {
new Thread(new Messager("Wallace")).start();
new Thread(new Messager("Gromit")).start();
}
private String name;
public Messager(String name) { this.name = name; }
public void run() {
message(1); message(2);
}
private synchronized void message(int n) {
System.out.print(name + "-" + n + " ");
}
}
我知道 synchronized 关键字使线程依赖于对象的锁。问题：
a) 标记为 synchronized 的方法完成后，锁是否会立即释放？或者一旦线程的 run() 方法完成 b) 我能否确保任何一个线程都会在另一个线程之前打印其名称和 1 2 ？
Given this code:
public class Messager implements Runnable {
public static void main(String[] args) {
new Thread(new Messager("Wallace")).start();
new Thread(new Messager("Gromit")).start();
}
private String name;
public Messager(String name) { this.name = name; }
public void run() {
message(1); message(2);
}
private synchronized void message(int n) {
System.out.print(name + "-" + n + " ");
}
}
I understand that the synchronized keyword makes the thread dependent on the object's lock. Questions:
a) Is the lock released as soon as the method marked as synchronized finishes? Or as soon as the thread's run() method finishes
b) Can I ensure that any one of the threads will print its name and 1 2 before the other?
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答：是的。
synchronized函数完成后就会立即释放。B、是的。可以，但如果您想这样做，为什么首先要编写多线程代码呢？
synchronized保证原子性，而不是与顺序有关的任何内容，但您可以通过等待标志更改来强制执行顺序。不管怎样，你想要强制执行的是顺序性。您可以在单线程环境中免费获得它:)A. Yes. It's released as soon as the
synchronizedfunction finishes.B. Yes. You can, but if you wanted to do so, why would you write multithreaded code in the first place?
synchronizedguarantees atomicity, not anything regarding the order, but you can enforce order by waiting for a flag to change. Anyway, what you are trying to enforce is sequentiality. You get this for free in single-threaded environments :)