Java中的異常處理

Question

我對嘗試，捕獲以及最終在Java中有疑問。 請考慮以下情形：

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!");
}

上面的代碼片段的輸出是什么？ 我要看的是：

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

還是會

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

還是僅僅（因為我們在catch塊中有投擲）

Line 1: IOException Encountered!

基本上，我沒有找到在catch塊中有一個“拋出”並最終在catch塊之后的塊的示例（如上面的示例）。 任何人都可以闡明它嗎？

謝謝。

Answer 1

引用Java語言規范§14.20.4 ：

通過首先執行try塊來執行帶有finally塊的try語句。 然后有一個選擇：

* 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). 

Answer 2

您將看到第一個。 最終塊將始終執行並最后執行。

Answer 3

這是流行測驗嗎？ 開玩笑。 如果有例外，您將看到第一個。 finally塊語句將始終被執行，因此將始終打印該語句。