带资源的try语句块介绍

在我们使用try() catch(){}的时候，如果涉及到流操作，经常需要关闭流比如：

 1         File file = new File("C:/Users/test.done");
        File newFile = new File(file.getAbsolutePath().replaceAll("\\.done$",".txt"));
        BufferedReader bufferedReader = null;
        BufferedWriter bufferedWriter = null;
        String line = "";
        try {
            bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
            bufferedWriter = new BufferedWriter(new FileWriter(newFile));
            while ((line = bufferedReader.readLine()) != null) {
                bufferedWriter.write(line+System.lineSeparator());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            if(null != bufferedReader){
                try {
                    bufferedReader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            if(null != bufferedWriter){
                try {
                    bufferedWriter.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
29         }

代码比较繁琐且很不方便，因此有简化的写法：

　　　　 File file = new File("C:/Users/test.done");
        File newFile = new File(file.getAbsolutePath().replaceAll("\\.done$",".txt"));
        String line = "";
        try(BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(file)));
                BufferedWriter bufferedWriter = new BufferedWriter(new FileWriter(newFile));) {
            while ((line = bufferedReader.readLine()) != null) {
                bufferedWriter.write(line+System.lineSeparator());
            }
        } catch (Exception e) {
            e.printStackTrace();
        } 

这种带资源的try语句（try-with-resource）在try块退出时，会自动调用bufferedReader.close()和bufferedWriter.close()方法，关闭资源，是不是很方便。