The finally Blockfinally块

The finally block always executes when the try block exits.当try块退出时，finally块始终执行。This ensures that the finally block is executed even if an unexpected exception occurs.这确保即使发生意外异常，也会执行finally块。But finally is useful for more than just exception handling — it allows the programmer to avoid having cleanup code accidentally bypassed by a return, continue, or break.但最后，它不仅适用于异常处理—它允许程序员避免因返回、继续或中断而意外绕过清理代码。Putting cleanup code in a finally block is always a good practice, even when no exceptions are anticipated.将清理代码放在finally块中始终是一种好的做法，即使在没有预期异常的情况下也是如此。

The try block of the writeList method that you've been working with here opens a PrintWriter.您在此处使用的writeList方法的try块将打开一个PrintWriter。The program should close that stream before exiting the writeList method.程序应该在退出writeList方法之前关闭该流。This poses a somewhat complicated problem because writeList's try block can exit in one of three ways.这带来了一个有点复杂的问题，因为writeList的try块可以通过以下三种方式之一退出。

1. The new FileWriter statement fails and throws an IOException.new FileWriter语句失败并引发IOException。
2. The list.get(i) statement fails and throws an IndexOutOfBoundsException.list.get(i)语句失败并抛出IndexOutOfBoundsException。
3. Everything succeeds and the try block exits normally.所有操作都成功，try块正常退出。

The runtime system always executes the statements within the finally block regardless of what happens within the try block.运行时系统始终在finally块中执行语句，而不管try块中发生了什么。So it's the perfect place to perform cleanup.所以这是进行清理的最佳场所。

The following finally block for the writeList method cleans up and then closes the PrintWriter.以下writeList方法的finally块将清理并关闭PrintWriter。

finally {
    if (out != null) { 
        System.out.println("Closing PrintWriter");
        out.close(); 
    } else { 
        System.out.println("PrintWriter not open");
    } 
}