Can we use “return” in finally block [duplicate]

问题:

This question already has answers here:

Returning from a finally block in Java (5 answers)

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

Closed 6 years ago.

Can we use return statement in finally block. Can this cause any problem?

回答1:

Returning from inside a finally block will cause exceptions to be lost.

A return statement inside a finally block will cause any exception that might be thrown in the try or catch block to be discarded.

According to the Java Language Specification:

If execution of the try block completes abruptly for any other reason R, then the finally block is executed, and then there is a choice:

   If the finally block completes normally, then the try statement
   completes  abruptly for reason R.

   If the finally block completes abruptly for reason S, then the try
   statement  completes abruptly for reason S (and reason R is
   discarded).

Note: As per JLS 14.17 - a return statement always completes abruptly.

回答2:

Yes you can write the return statement in a finally block and it will override the other return value.

EDIT:
For example in below code

public class Test {

    public static int test(int i) {
        try {
            if (i == 0)
                throw new Exception();
            return 0;
        } catch (Exception e) {
            return 1;
        } finally {
            return 2;
        }
    }

    public static void main(String[] args) {
        System.out.println(test(0));
        System.out.println(test(1));
    }
}

The output is always 2, as we are returning 2 from the finally block. Remember the finally always executes whether there is a exception or not. So when the finally block runs it will override the return value of others. Writing return statements in finally block is not required, in fact you should not write it.

回答3:

Yes you can,But you should not 1 ,because the finally block is meant for a special purpose.

finally is useful for more than just exception handling — it allows the programmer to avoid having cleanup code accidentally bypassed by a return, continue, or break. Putting cleanup code in a finally block is always a good practice, even when no exceptions are anticipated.

Writing your logic inside it is not recommended.

回答4:

You can write return statement in finally block but the value returned from try block will be updated on the stack and not the finally block return value.

Let us say you have this function

private Integer getnumber(){
Integer i = null;
try{
   i = new Integer(5);
   return i;
}catch(Exception e){return 0;}
finally{
  i = new Integer(7);
  System.out.println(i);
}
}

and you are calling this from main method

public static void main(String[] args){
   System.out.println(getNumber());
}

This prints

7
5