A singleton pattern, to make the Mock of it easily

MyManager.java

public class MyManager {
    private MyManager() {}

    public static MyManager getInstance() {
 
        return Singleton.getInstance(MyManager.class);
  
    }

    public void myMethod() {
    }
}

Singleton.java

public class Singleton {
    private static final Map<Class, Object> SINGLETONS = new HashMap<>();
    private Singleton() { }

    public static synchronized <T> T getInstance(Class<T> clazz) {
        T instance = (T) SINGLETONS.get(clazz);
        if (instance == null) {
            try {
                instance = createInstance(clazz);
                setInstance(clazz, instance);
            } catch (Exception e) {
                VLog.e(e);
            }
        }
        return instance;
    }

    public static <T> void setInstance(Class<T> clazz, T instance) {
        SINGLETONS.put(clazz, instance);
    }

    public static void clear() {
        SINGLETONS.clear();
    }

    @NonNull
    private static <T> T createInstance(Class<T> clazz)
            throws IllegalAccessException, NoSuchMethodException,
            InstantiationException, InvocationTargetException {
        Constructor<T> constructor = clazz.getDeclaredConstructor();
        constructor.setAccessible(true);
        return constructor.newInstance();
    }
}