对单例类进行弱引用的正确方法是什么

import java.lang.ref.WeakReference;

public class Singleton {
    private static WeakReference<Singleton> instance = null;

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

    public static Singleton getInstance() {
        if (instance == null || instance.get() == null) {
            synchronized (Singleton.class) {
                if (instance == null || instance.get() == null) {
                    instance = new WeakReference<>(new Singleton());
                }
            }
        }
        return instance.get();
    }
}