如何修复私有构造函数的Sonar问题？

public class MyClass {
    private MyClass() {
        // 私有构造函数
    }

    public static MyClass getInstance() {
        return new MyClass();
    }
}

public class Singleton {
    private static Singleton instance;

    private Singleton() {
        // 私有构造函数
    }

    public static Singleton getInstance() {
        if (instance == null) {
            instance = new Singleton();
        }
        return instance;
    }
}

public class MyClass {
    private MyClass() {
        // 私有构造函数
    }

    private static class Holder {
        private static final MyClass instance = new MyClass();
    }

    public static MyClass getInstance() {
        return Holder.instance;
    }
}