CODEWITHSUNDEEP
javatry-catch
Rohan RM
Rohan RM

Reputation: 157

How to make final variables declared in a try block to be used in catch / finally block?

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;
}

The variable fileReader and bufferedReader declared as final in try block cannot be used in finally block. I can't declare them outside try block, because they might throw exception. I want the variables to be final too.

Upvotes: 0

Views: 338

Answers (2)

Maurice Perry
Maurice Perry

Reputation: 9650

Since Java 7, you can write things like that:

public StringBuffer readFile(final File inputFile) {
    String tempLine; // variable declaration
    Logger log = Logger.getLogger("Error Message");
    final StringBuffer content = new StringBuffer();
    try (final FileReader fileReader = new FileReader(inputFile);
            final BufferedReader bufferedReader = new BufferedReader(fileReader)){        
        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);
    }
    return content;
}

Here fileReader and bufferedReader are implicitly closed.

Upvotes: 0

rechandler
rechandler

Reputation: 768

If you use at least Java 7 you can use try-with-resources Statement to close your resources. Here's the code:

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;
}

Upvotes: 1

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