Since in Java optional parameters are not possible, I tried to create 2 constructors.

public class Tts {
    public Context context;
    private final MediaPlayer _mediaPlayer;
    private final CopyBarVisualizer _barTop;
    private final CopyBarVisualizer _barBottom;

    public Tts(Context context) {
        this.context = context;
    }

    public Tts(Context context, MediaPlayer _mediaPlayer, BarVisualizer _barTop, BarVisualizer _barBottom) {
        this.context = context;
        this._mediaPlayer = _mediaPlayer;
        this._barTop = (CopyBarVisualizer) _barTop;
        this._barBottom = (CopyBarVisualizer) _barBottom;
    }
}

Now my problems are the private properties. There I get the error

Variable '_mediaPlayer' might not have been initialized

In another method, I want to check if the properties are set. But how can I avoid these errors?

CodePudding user response：

To resolve the error, you can:

Delete final keyword in attributes

public class Tts {
    public Context context;
    private MediaPlayer _mediaPlayer;
    private CopyBarVisualizer _barTop;
    private CopyBarVisualizer _barBottom;

    public Tts(Context context) {
        this.context = context;
    }

    public Tts(Context context, MediaPlayer _mediaPlayer, BarVisualizer _barTop, BarVisualizer _barBottom) {
        this.context = context;
        this._mediaPlayer = _mediaPlayer;
        this._barTop = (CopyBarVisualizer) _barTop;
        this._barBottom = (CopyBarVisualizer) _barBottom;
    }
}

Give a default null value to your final attributes

public class Tts {
    public Context context;
    private final MediaPlayer _mediaPlayer; 
    private final CopyBarVisualizer _barTop; 
    private final CopyBarVisualizer _barBottom; 

    public Tts(Context context) {
        this(context, null, null, null); // to solve the error problem
    }

    public Tts(Context context, MediaPlayer _mediaPlayer, BarVisualizer _barTop, BarVisualizer _barBottom) {
        this.context = context;
        this._mediaPlayer = _mediaPlayer;
        this._barTop = (CopyBarVisualizer) _barTop;
        this._barBottom = (CopyBarVisualizer) _barBottom;
    }
}

This code is from @Khahani

For optional attributes in your class you can use Builder pattern :

public class TtsBuilder{
    public Context context;
    private MediaPlayer _mediaPlayer = null;
    private BarVisualizer _barTop = null;
    private BarVisualizer _barBottom = null;

    public TtsBuilder(Context context) {
        this.context = context;
    }

    public TtsBuilder withMediaPlayer(MediaPlayer _mediaPlayer) {
        this._mediaPlayer = _mediaPlayer;
        return this;
    }

    public TtsBuilder withBarTop(BarVisualizer _barTop) {
        this._barTop = _barTop;
        return this;
    }

    public TtsBuilder withBarBottom(BarVisualizer _barBottom) {
        this._barBottom = _barBottom;
        return this;
    }

    public Tts build() {
        return new Tts(context, _mediaPlayer, _barTop, _barBottom);
    }
}

Example :

public static void main(String[] args){
    Tts ttsMedia = new Tts(aContext).withMediaPlayer(aMediaPlayer).build();
    Tts ttsBarTopBottom = new Tts(aContext)
            .withBarTop(aBarTop)
            .withBarBottom(aBarBottom)
            .build();
}

Note

The naming convention in Java recommends:

Variable names should not start with underscore _ or dollar sign $ characters, even though both are allowed.

For more details you can check Oracle documentation.

CodePudding user response：

If you want to solve the error problem, you can fix it with the code below; however, when the constructor initializes final fields, you can't change them, so probably it's better to remove the final keyword.

public class Tts {
    public Context context;
    private final MediaPlayer _mediaPlayer; 
    private final CopyBarVisualizer _barTop; 
    private final CopyBarVisualizer _barBottom; 

    public Tts(Context context) {
        this(context, null, null, null); // to solve the error problem
    }

    public Tts(Context context, MediaPlayer _mediaPlayer, BarVisualizer _barTop, BarVisualizer _barBottom) {
        this.context = context;
        this._mediaPlayer = _mediaPlayer;
        this._barTop = (CopyBarVisualizer) _barTop;
        this._barBottom = (CopyBarVisualizer) _barBottom;
    }
}