Java:使用Singletons和泛型设计

public class Singleton {
    private static Singleton instance;

    private Singleton() {
        // 构造函数私有化
    }

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

public class GenericClass<T> {
    private T data;

    public void setData(T data) {
        this.data = data;
    }

    public T getData() {
        return data;
    }
}

GenericClass<String> stringClass = new GenericClass<>();
stringClass.setData("Hello, world!");
String data = stringClass.getData();