同步正常工作在這個代碼:爲什麼同步在第二個代碼中不起作用?
class PrintNumbers {
synchronized public void display() {
System.out.println("in display");
for (int i = 0; i < 3; i++) {
System.out.println("Thread name : "+ Thread.currentThread().getName() + " i= " + i);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.getMessage();
}
}
System.out.println("out of display");
}
}
class MyThread implements Runnable {
Thread t;
PrintNumbers printNumbers;
MyThread(PrintNumbers printNumbers, String s) {
this.printNumbers = printNumbers;
t = new Thread(this,s);
t.start();
}
public void run() {
printNumbers.display();
}
}
class SyncExample {
public static void main(String[] args) {
PrintNumbers printNumbers = new PrintNumbers();
new MyThread(printNumbers, "My Thread 1");
new MyThread(printNumbers, "My Thread 2");
}
}
輸出:
in display
Thread name : My Thread 1 i= 0
Thread name : My Thread 1 i= 1
Thread name : My Thread 1 i= 2
out of display
in display
Thread name : My Thread 2 i= 0
Thread name : My Thread 2 i= 1
Thread name : My Thread 2 i= 2
out of display
但不是在這個代碼:
class PrintNumbers {
synchronized public void display() {
System.out.println("in display");
for (int i = 0; i < 3; i++) {
System.out.println("Thread name : "+ Thread.currentThread().getName() + " i= " + i);
try {
Thread.sleep(1000);
} catch (InterruptedException e) {
e.getMessage();
}
}
System.out.println("out of display");
}
}
class MyThread implements Runnable {
Thread t;
PrintNumbers printNumbers;
MyThread(String s) {
this.printNumbers = new PrintNumbers();
t = new Thread(this,s);
t.start();
}
public void run() {
printNumbers.display();
}
}
class SyncExample {
public static void main(String[] args) {
new MyThread("My Thread 1");
new MyThread("My Thread 2");
}
}
輸出:
in display
Thread name : My Thread 1 i= 0
in display
Thread name : My Thread 2 i= 0
Thread name : My Thread 1 i= 1
Thread name : My Thread 2 i= 1
Thread name : My Thread 2 i= 2
Thread name : My Thread 1 i= 2
out of display
out of display
我不明白什麼區別wrt同步是否在可運行MyThread和SyncExample類中初始化PrintNumbers。請解釋。
非靜態同步方法在'this'上進行同步。 – tkausl
第二,你需要'display'方法是靜態的,它們鎖定了2個對象。 – passion
您正在使用PrintNumbers的差異對象,鎖定位於對象級別。這就是爲什麼你得到不同的輸出。 – cody123