Java Generics Copy构造函数

Question

我想为一般定义的类编写一个拷贝构造函数.我有一个内部类Node,我将其用作二叉树的节点.当我传入一个新的对象时

public class treeDB <T extends Object> {
    //methods and such

    public T patient; 
    patient = new T(patient2);       //this line throwing an error
    //where patient2 is of type <T>
}

我只是不知道如何一般地定义一个复制构造函数.

Answer 1

T不能保证它所代表的类将具有所需的构造函数,因此您无法使用new T(..)表单.

我不确定这是否是你需要的但如果你确定要复制的对象类将有复制构造函数那么你可以使用像

public class Test<T> {

    public T createCopy(T item) throws Exception {// here should be
        // thrown more detailed exceptions but I decided to reduce them for
        // readability

        Class<?> clazz = item.getClass();
        Constructor<?> copyConstructor = clazz.getConstructor(clazz);

        @SuppressWarnings("unchecked")
        T copy = (T) copyConstructor.newInstance(item);

        return copy;
    }
}

//demo for MyClass that will have copy constructor: 
//         public MyClass(MyClass original)
public static void main(String[] args) throws Exception {
    MyClass mc = new MyClass("someString", 42);

    Test<MyClass> test = new Test<>();
    MyClass copy = test.createCopy(mc);

    System.out.println(copy.getSomeString());
    System.out.println(copy.getSomeNumber());
}