java中return和finally的执行问题

1. try中有return：先执行try代码块，return语句或者函数也先执行，然后执行finally语句，最后执行try中的return返回结果。

public class FinallyTest1 {

    public static void main(String[] args) {
        
        System.out.println(test11());
    }
    
    public static String test11() {
        try {
            System.out.println("try block");

           return test12();
      } finally {
           System.out.println("finally block");
       }
  }

  public static String test12() {
       System.out.println("return statement");

       return "after return";
   }
    
}

结果：

try block
return statement
finally block
after return

2. try中和finally中都有return，finally中return会覆盖try中return

public class FinallyTest2 {

    public static void main(String[] args) {

        System.out.println(test2());
    }

    public static int test2() {
        int b = 20;

        try {
            System.out.println("try block");

            return b += 80;
        } catch (Exception e) {

            System.out.println("catch block");
        } finally {

            System.out.println("finally block");

            if (b > 25) {
                System.out.println("b>25, b = " + b);
            }

            return 200;
        }

    }

}

结果：

try block
finally block
b>25, b = 100
200

3. 如果finally中没有return语句，只是修改返回值的语句，那么结果可能被修改也可能不会。如果try中return简单的值类型，finally中修改无效，如果try中return一个对象，finally中可以操作该对象。

public class FinallyTest3 {

    public static void main(String[] args) {

        System.out.println(test3());
    }

    public static int test3() {
        int b = 20;

        try {
            System.out.println("try block");

            return b += 80;
        } catch (Exception e) {

            System.out.println("catch block");
        } finally {

            System.out.println("finally block");

            if (b > 25) {
                System.out.println("b>25, b = " + b);
            }

            b = 150;
        }

        return 2000;
    }
}

结果：

try block
finally block
b>25, b = 100
100

public class FinallyTest6
{
    public static void main(String[] args) {
        System.out.println(getMap().get("KEY").toString());
    }
     
    public static Map<String, String> getMap() {
        Map<String, String> map = new HashMap<String, String>();
        map.put("KEY", "INIT");
         
        try {
            map.put("KEY", "TRY");
            return map;
        }
        catch (Exception e) {
            map.put("KEY", "CATCH");
        }
        finally {
            map.put("KEY", "FINALLY");
            map = null;
        }
         
        return map;
    }
}

结果：

FINALLY

4. try中发送异常的时候，try中的return语句不会执行，但是return行为会最后执行，catch和finally会执行并且会改变结果，因为被异常捕获，try-catch-finnaly块外面的return永远不会被执行。

public class FinallyTest4 {

    public static void main(String[] args) {

        System.out.println(test4());
    }

    public static int test4() {
        int b = 20;

        try {
            System.out.println("try block");

            b = b / 0;

            return b += 80;
        } catch (Exception e) {

            b += 15;
            System.out.println("catch block");
        } finally {

            System.out.println("finally block");

            if (b > 25) {
                System.out.println("b>25, b = " + b);
            }

            b += 50;
        }

        return 204;
    }

}

结果：

try block
catch block
finally block
b>25, b = 35
85

5. catch中如果有return，情况跟try中的return一致

public class FinallyTest5 {

    public static void main(String[] args) {

        System.out.println(test5());
    }

    public static int test5() {
        int b = 20;

        try {
            System.out.println("try block");
            
            b = b /0;

            return b += 80;
        } catch (Exception e) {

            System.out.println("catch block");
            return b += 15;
        } finally {

            System.out.println("finally block");

            if (b > 25) {
                System.out.println("b>25, b = " + b);
            }

            b += 50;
        }

    }

}

结果：

try block
catch block
finally block
b>25, b = 35
35

参考文章：
Java finally语句到底是在return之前还是之后执行