java - 错误: variable might not have been initialized

Question

我无法找到我得到的原因:

variable might not have been initialized

示例1:

class Test {
    public static void main(String[] args) {
        int i = 10;
        int j;
        if (i == 10) {
            j = 20;
        }
        System.out.println(j);
    }
}

Test.java:11: error: variable j might not have been initialized
System.out.println(j);
                   ^
1 error

示例2:

class Test {
    public static void main(String[] args) {
        int i = 10;
        int j;
        if (i == 10) {
            j = 20;
        } else {
            j = 30;
        }
        System.out.println(j);
    }
}

输出:

20

我的疑问是在第二个例子中，j是如何初始化的？

Answer 1

第一种情况，如果 i != 10 j 期间不会被初始化

System.out.println(j);

在第二个示例中，j 的值始终为 (i != 10 j 为 30)

System.out.println(j);

注意

**might not** be initialized