Java finally block 更改类变量的值，但不更改 Try block 中的 return 语句

Question

这个问题已经有答案了:

Why does changing the returned variable in a finally block not change the return value? (7 个回答)

已关闭 3 年前。

我已经看到这种行为被解释了，因为它通常是finally block 中的不可变字符串，但我不明白为什么int原语会这样表现。

“i”不作为方法中的参数按值传递。该方法是直接设置i类变量。这是显而易见的，因为在方法完成后打印时 i 的值发生了变化。

很明显，它在 try block 中的 return 语句之前已被更改，因为 finally block 中的打印首先打印。

public class Test {
    static int i = 0;
    public static void main(String[] args) {

        System.out.println("Try Block returns: " + methodReturningValue());
        System.out.println("Value of i after method execution is " + i);
    }


    static int methodReturningValue()
        {


            try
            {
                i = 1;
                System.out.println("try block is about to return with an i value of: "+  i);
                return i;
            }
            catch (Exception e)
            {
                i = 2;
                return i;
            }
            finally
            {
                i = 3;
                System.out.println("Finally block: i has been changed to 3");
            }
        }


    }

输出:

try block is about to return with an i value of: 1
Finally block: i has been changed to 3
Try Block returns: 1
Value of i after method execution is 3

Answer 1

是的，finally block 总是在“返回”和“抛出”异常之后运行，您的代码与:

public class Test {
    static int i = 0;
    public static void main(String[] args) {

        System.out.println(methodReturningValue());
        System.out.println(i);
    }


    static int methodReturningValue()
    {

        int answer = 0;
        try
        {
            i = 1;
            answer = i;
        }
        catch (Exception e)
        {
            i = 2;
            answer = i;
        }
        i = 3;
        System.out.println("i=3");
        return answer;
    }


}