代码
public class MyTest {
public static void main(String[] args) {// step 6
Singleton singleton = Singleton.getInstance();//step 7
System.out.println("counter1= " + singleton.counter1);
System.out.println("counter2= " + singleton.counter2);
}
}
class Singleton {
private static Singleton singleton = new Singleton();// step 1
public static int counter1; // step 2
public static int counter2 = 0;// step 3
private Singleton() {// step 4
counter1++;
counter2++;
}
public static Singleton getInstance() {// step 5
return singleton;
}
}
结果
counter1= 1
counter2= 0 奇怪的结果
执行顺序
6
a. 调用主入口的方法，首先加载MyTest类
b. 调用main方法
7.
a. 调用静态方法时，先初始化静态变量的默认值，再赋值
b. singleton 为null counter1为0 counter2 为0 赋默认值
c. 再赋值 = Singleton.getInstance(); 导致调用4 counter1为1 counter2 为1
d. 在赋值 counter1 没有赋值所以还是1 counter1 有赋值所以是0了
让结果变的正常
将1放到3的后面