DD and DU anomalys in function

Question

I recently started using PMD to keep my code clean and it's been going well, but I've run into a few problems in the following function.

private final void readFile() throws Exception{
    code.clear();
    imports.clear();

    //DD anomaly
    FileReader fileReader = null;
    BufferedReader bufferedReader = null;

    try{
        fileReader = new FileReader(file);
        bufferedReader = new BufferedReader(fileReader);

        String line;
        //DU anomaly 
        boolean code_started = false;
        //DU anomaly
        while((line = bufferedReader.readLine()) != null){
            if(code_started)    code.add(line);
            else{
                if(lineIsImport(line))
                    imports.add(line);
                else if(lineIsClassDeclaretion(line)){
                    code_started = true;
                    code.add(line);                     
                }
            }
        }
    }
    catch(FileNotFoundException fn_ex){
        throw new Exception("File not found!");
    }
    catch(IOException io_ex){
        throw new Exception("Failed to read file: " + file.getName() + "!");
    }
    finally{
        try{
            if(bufferedReader != null)  
                bufferedReader.close();
            if(fileReader != null)  
                fileReader.close();
        }
        catch(IOException io_ex){
            throw new Exception("Failed to close reader");
        }           
    }
}

The first DD anomaly:

FileReader fileReader = null;
BufferedReader bufferedReader = null;

If I don't set both to null the anomaly disappears, but I get an error in the finally block. I have no idea what the correct way of writing this should be.

Next is the DU anomaly:

boolean code_started = false;

If I don't set the variable the anomaly disappears, but again an error a few lines down.

The last is a DU anomaly:

while((line = bufferedReader.readLine()) != null)

This anomaly is probably the same as the one above, but again I have no idea how to fix it.

I would be grateful if somebody could explain or show how to write this function in a manner that won't cause PMD to show the anomaly.

Answer 1

If you are using Java 7 or higher you can try-with-resources. The try-with-resources statement ensures that each resource is closed at the end of the statement. Below is the example how you can use it.

Go Through: https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html for more info.

        File file = null;
        //Automatically closes resources try-with-resources block
        try( FileReader fileReader = new FileReader(file);BufferedReader bufferedReader = new BufferedReader(fileReader);){
            String line;
            boolean code_started = false;
            while((line = bufferedReader.readLine()) != null){
               //Code Goes Here
            }
        }catch(FileNotFoundException fn_ex){
            throw new Exception("File not found!");
        }
        catch(IOException io_ex){
            throw new Exception("Failed to read file: " + file.getName() + "!");
        }