Java中的異常處理

Question

我有關於try，catch和最後在Java中的問題。考慮以下情形：

try{ 
//Some code here that throws IOExceotion 
} 
catch (IOException ex){ 
System.out.println("Line 1: IOException Encountered!"); 
throw ex; 
} 
finally { 
System.out.println("Line 2: I am always executed!"); 
} 

上面的代碼段的輸出是什麼？ 我要去看看：

Line 1: IOException Encountered! 
Line 2: I am always executed! 

還是會

Line 2: I am always executed! 
Line 1: IOException Encountered! 

或將它只是（因爲我們在catch塊一丟）

Line 1: IOException Encountered! 

基本上，我還沒有找到一個例子，在catch塊中有一個「throw」，最後是catch塊之後的塊（就像上面的例子）。任何人都可以點亮它嗎？

謝謝。

Answer 1

你會看到第一個。最後，塊始終執行並作爲最後一個。

Answer 2

這是一個流行測驗嗎？開玩笑。如果有異常，你會看到第一個。 finally語句總是會被執行，所以會一直打印。

Answer 3

引述Java Language Specification, §14.20.4：

一個try語句具有finally塊，先執行try塊執行。然後有一個選擇：

* If execution of the try block completes normally, then the finally block is executed, and then there is a choice: 
     o If the finally block completes normally, then the try statement completes normally. 
     o If the finally block completes abruptly for reason S, then the try statement completes abruptly for reason S. 
* If execution of the try block completes abruptly because of a throw of a value V, then there is a choice: 
     o If the run-time type of V is assignable to the parameter of any catch clause of the try statement, then the first (leftmost) such catch clause is selected. The value V is assigned to the parameter of the selected catch clause, and the Block of that catch clause is executed. Then there is a choice: 
      + If the catch block completes normally, then the finally block is executed. Then there is a choice: 
        # If the finally block completes normally, then the try statement completes normally. 
        # If the finally block completes abruptly for any reason, then the try statement completes abruptly for the same reason. 
      + If the catch block completes abruptly for reason R, then the finally block is executed. 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). 
     o If the run-time type of V is not assignable to the parameter of any catch clause of the try statement, then the finally block is executed. Then there is a choice: 
      + If the finally block completes normally, then the try statement completes abruptly because of a throw of the value V. 
      + If the finally block completes abruptly for reason S, then the try statement completes abruptly for reason S (and the throw of value V is discarded and forgotten). 
* If execution of the try block completes abruptly for any other reason R, then the finally block is executed. Then there is a choice: 
     o If the finally block completes normally, then the try statement completes abruptly for reason R. 
     o If the finally block completes abruptly for reason S, then the try statement completes abruptly for reason S (and reason R is discarded).