使用“最后”的好处是什么？在java中的try-catch块之后？ [英] What is the benefit to use "finally" after try-catch block in java?

问题描述

当try-catch结束时，总是会执行finally块，无论是否异常。
但是，try-catch之外和之后的每一行代码都会被执行。
那么，我为什么要使用finally语句呢？

The "finally" block is always executed when the try-catch ends, either in case of exception or not. But also every line of code outside and after the try-catch is always executed. So, why should I use the finally statement?

示例：

try {
    //code...
} catch (Exception e) {
    //code...
} finally {
    System.out.println("This line is always printed");
}
System.out.println("Also this line is always printed !! So why to use 'finally'?? ");

推荐答案

最有用的情况是你需要释放一些资源：

The most useful case is when you need to release some resources :

InputStream is = ...
try {
    //code...
} catch (Exception e) {
    //code...
} finally {
    is.close();
}

更一般地说，当你想确定你的代码被执行时，你会使用它最后，即使执行期间有异常：

More generally, you use it when you want to be sure your code is executed at the end, even if there was an exception during execution :

long startTime = System.currentTimeMillis();
try {
    //code...
} catch (Exception e) {
    //code...
} finally {
    long endTime = System.currentTimeMillis();
    System.out.println("Operation took " + (endTime-startTime) + " ms");
}

这个的想法终于阻止始终执行是因为整个区块后面的第一行不是这种情况

The idea of this finally block always being executed is that it's not the case for the first line following the whole block

• 如果 catch 块允许一些throwable传递


• 如果它重新抛出一个异常，这是非常频繁的

• if the catch block lets some throwable pass
• if it rethrows itself an exception, which is very frequent

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