When should I use the finally-block in Java's try-catch-finally

问题

When should I use code snippet A instead of snippet B (i.e. what are the benefits of using snippet A)?:

Snippet A:

try {
    // codeblock A
}
catch (Exception ex) {
    // codeblock B
}
finally {
    //codeblock C
}

Snippet B:

try {
    // codeblock A
}
catch (Exception ex) {
    // codeblock B
}

//codeblock C

回答1:

Use a finally block if you have code that must execute regardless of whether or not an exception is thrown.

Cleaning up scarce resources like database connections are a good example.

回答2:

An obvious case is when you re-raise or throw another exception in your catch block.

回答3:

It's useful if you need to do some cleanup, e.g. close a database connection. Because "finally" is executed always, you don't need to do the bug-prone copy-paste of the same code in the end of the "try" and in also in one or more "catch" blocks.

回答4:

You must almost always use the snippet with finally block when you have resources that needs clean up in both successful or error scenarios. A typical example is the jdbc connection object which should always be closed (clean up) in the finally block.

回答5:

Imagine to have a return statement inside the catch block: the C block will not be executed in snippet B, but in snippet A it will, before returning.

来源：https://stackoverflow.com/questions/7405702/when-should-i-use-the-finally-block-in-javas-try-catch-finally