java - 从finally block 返回一个值

Question

这个问题已经有答案了:

Multiple returns: Which one sets the final return value? (7 个回答)

已关闭 8 年前。

我在一个java认证网站上找到了这段代码

   public class Test1{
        public static void main(String args[]){
            System.out.println(method());
        }
        public static int method(){
           try{
              return 1;
           }
           catch(Exception e){
              return 2;
           }
           finally{
              return 3;
           }
        }
    }

所以这段代码的输出结果如3所示。这怎么可能……因为它在 try block 本身中返回 1？代码永远不会到达finally，对吗？

Answer 1

代码永远不会到达finally，对吗？不，如果有finally block 控制会在try或/and catch之后转到finally

因为无论如何finally总会执行。除了 Mike Kobit 所说的System.exit

感谢 Jason C，来自 JLS 14.17. The return Statement

It can be seen, then, that a return statement always completes abruptly.

The preceding descriptions say "attempts to transfer control" rather than just "transfers control" because if there are any try statements (§14.20) within the method or constructor whose try blocks or catch clauses contain the return statement, then any finally clauses of those try statements will be executed, in order, innermost to outermost, before control is transferred to the invoker of the method or constructor. Abrupt completion of a finally clause can disrupt the transfer of control initiated by a return statement.

来自JLS 14.20.2. Execution of try-finally and try-catch-finally

If execution of the try block completes normally, then the finally block is executed, and then there is a choice:

1. If the finally block completes normally, then the try statement completes normally.
2. If the finally block completes abruptly for reason S, then the try statement completes abruptly for reason S.

因此，在您的代码中，try 返回 1，然后控制转到最终返回 3。因此函数的返回值将为 3。