AWTUI.java

public class AWTUI implements UIPlug, XLetStateListener {
    static AWTUI instance = null;
    // ...
    
    AWTUI(/* params */) {
        // ...
    }

    public synchronized static AWTUI getInstance() {
        if (instance == null) {
            // ...
            instance = new AWTUI(/* params */);
        }
        return instance;
    }
    // ...
}