java - 如何使在 try block 中声明的最终变量在 catch/finally block 中使用？

Question

public StringBuffer readFile(final File inputFile) {
    String tempLine; // variable declaration
    Logger log = Logger.getLogger("Error Message");
    try {
        final FileReader fileReader = new FileReader(inputFile);
        final BufferedReader bufferedReader = new BufferedReader(fileReader);
        final StringBuffer content = new StringBuffer();
        while((tempLine=bufferedReader.readLine())!=null) {
            content.append(tempLine);
            content.append(System.getProperty("line.separator"));
        }
    }
    catch(FileNotFoundException e) {
        log.log(Level.WARNING, "File not found", e);
    }
    catch (IOException e) {
        log.log(Level.WARNING, "Couldn't Read file", e);
    }
    finally {
        bufferedReader.close();
        fileReader.close();
    }
    return content;
}

在try block 中声明为final的变量fileReader和bufferedReader不能在finally block 中使用。我不能在 try block 之外声明它们，因为它们可能会引发异常。我也希望变量是最终的。

Answer 1

如果您至少使用 Java 7，则可以使用 try-with-resources Statement关闭您的资源。代码如下:

public StringBuffer readFile(final File inputFile) {
    String tempLine; // variable declaration
    Logger log = Logger.getLogger("Error Message");
    try (final FileReader fileReader = new FileReader(inputFile)) {
        try (final BufferedReader bufferedReader = new BufferedReader(fileReader)) {
            final StringBuffer content = new StringBuffer();
            while((tempLine=bufferedReader.readLine())!=null) {
                content.append(tempLine);
                content.append(System.getProperty("line.separator"));
            }

            return content;
        }
    } catch (FileNotFoundException e) {
        log.log(Level.WARNING, "File not found", e);
    } catch (IOException e) {
        log.log(Level.WARNING, "Couldn't Read file", e);
    }
    // return null or throw exception;
}