return in try-catch

1. Case 1 (there is return in try, but there is no return in finally):
public class TryTest{
public static void main(String[] args){
System.out.println(test());
}

private static int test(){int num = 10;try{System.out.println("try");return num += 80;}catch(Exception e){System.out.println("error");}finally{if (num > 20){System.out.println("num>20 : " + num);}System.out.println("finally");}return num;}

}

2. Case 2 (return in both try and finally):
public class TryTest{
public static void main(String[] args){
System.out.println(test());
}

 private static int test(){int num = 10;try{System.out.println("try");return num += 80;}catch(Exception e){System.out.println("error");}finally{if (num > 20){System.out.println("num>20 : " + num);}System.out.println("finally");num = 100;return num;}}}

3. Case 3 (change the return value num in finally):
public class TryTest{
public static void main(String[] args){
System.out.println(test());
}

private static int test(){int num = 10;try{System.out.println("try");return num;}catch(Exception e){System.out.println("error");}finally{if (num > 20){System.out.println("num>20 : " + num);}System.out.println("finally");num = 100;}return num;}

}
4. Case 4 (wrapping the value of num in the Num class):

public class TryTest{
public static void main(String[] args){
System.out.println(test().num);
}

private static Num test(){Num number = new Num();try{System.out.println("try");return number;}catch(Exception e){System.out.println("error");}finally{if (number.num > 20){System.out.println("number.num>20 : " + number.num);}System.out.println("finally");number.num = 100;}return number;}

}

class Num{
public int num = 10;
}

1.
The output result is as follows:
try
num>20 : 90
finally
90

Analysis: Obviously "return num += 80" is split into two statements "num = num+80" and "return num", the line executes the "num = num+80" statement in try,Save it, before the "return num" in try is executed, execute the statement in finally, and then return 90.
2.
The output is as follows:

try
num>20 : 90
finally
100

Analysis: The return statement in try is also split, and the return statement in finally is executed before the return statement in try, so the return statement in try is "overwritten" and is no longer executed.
3.
The output result is as follows:
try

finally

10

Analysis: Although the return value num is changed in finally, because the value of num is not returned in finally, after executing the statement in finally, the test() function will get the value of num returned in try,The value of num in try is still the value reserved before the program enters the finally code block, so the return value obtained is 10.
4.
The output is as follows:
try
finally
100

It can be seen from the results that the value of the return value num is also changed in finally. In case 3, it is not returned by the return in try (the test() method does not get 100), but hereIt was returned by the return statement in try.

Summary:
The try statement executes all other operations before returning, retains the value to be returned, and then transfers to execute the statement in finally, and then it is divided into the following three cases:

Situation 1: If there is a return statement in finally, the return statement in try will be "overwritten", and the return statement in finally will be directly executed to get the return value, so that it will not be able to get the good reserved before tryreturn value.Case 2: If there is no return statement in finally, and the return value has not been changed, after the statement in finally is executed, the return statement in try will be executed, and the previously reserved value will be returned.Case 3: If there is no return statement in finally, but the value to be returned is changed, this is somewhat similar to the difference between pass-by-reference and pass-by-value, which can be divided into the following two cases:1) If the return data is a basic data type or a text string, the changes to the basic data in finally have no effect, and the return statement in try will still return the value reserved before entering the finally block.2) If the return data is a reference data type, and the change of the attribute value of the reference data type in finally works, the return statement in try returns the value of the attribute changed in finally.