[javase] try-finally

[Alice52]

finally 中修改值得问题

1. 基本类型在 finally 中修改, 且之前已经返回, 则 finally 中的修改是无效的.

2. 引用类型在 finally 中修改, 且之前已经返回, 则 finally 中的修改是有效的.

3. finally 保护问题:

   • 如果 finally 中有 return 则不存在返回值保护;
   • 否则存在返回值保护, finally 无法修改 try 中的返回值[引用类型则是不能修改返回值地址]

4. sample code

   @Test
   public void testTry() {
       assert changeBasicInFinally() == 1;
       assert changeReferenceInFinally().name().equals("tim");
       assert returnBasicInFinally() == 2;
   }
   
   public int changeBasicInFinally() {
       int i;
       try {
           i = 1;
           return i;
       } finally {
           i = 2;
       }
   }
   
   public int returnBasicInFinally() {
       int i;
       try {
           i = 1;
           return i;
       } finally {
           i = 2;
           return i;
       }
   }
   
   public Person changeReferenceInFinally() {
       Person person = Person.builder().age(18).name("zack").build();
       try {
           return person;
       } finally {
           person.name("tim");
       }
   }