“范围”问题Java中try catch块中的变量 [英] Problem with "scopes" of variables in try catch blocks in Java

问题描述

有人可以解释为什么在最后几行中，br不被识别为变量？我甚至尝试将br放在 try子句中，将其设置为 final 等。这是否有任何内容Java不支持闭包吗？我99％有信心类似的代码可以在C＃中工作。

Could anyone explain me why in the last lines, br is not recognized as variable? I've even tried putting br in the try clause, setting it as final, etc. Does this have anything to do with Java not support closures? I am 99% confident similar code would work in C#.

private void loadCommands(String fileName) {
    try {
        final BufferedReader br = new BufferedReader(new FileReader(fileName));

        while (br.ready()) {
            actionList.add(CommandFactory.GetCommandFromText(this, br.readLine()));
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (br != null) br.close(); //<-- This gives error. It doesn't
                                    // know the br variable.
    }       
}

谢谢

推荐答案

因为它在try块中声明。在一个块中声明的局部变量在其他块中是不可访问的，除非包含在其中，即，当块结束时变量超出范围。这样做：

Because it's declared in the try block. Local variables are declared in one block are inaccessible in other blocks except if contained in it, i.e., the variables go out of scope when their block ends. Do this:

private void loadCommands(String fileName) {
    BufferedReader br = null;
    try {
        br = new BufferedReader(new FileReader(fileName));

        while (br.ready()) {
            actionList.add(CommandFactory.GetCommandFromText(this, br.readLine()));
        }
    } catch (FileNotFoundException e) {
        e.printStackTrace();
    } catch (IOException e) {
        e.printStackTrace();
    } finally {
        if (br != null) try { br.close(); } catch (IOException logOrIgnore) {}
    }       
}

这篇关于“范围”问题Java中try catch块中的变量的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！