📅  最后修改于: 2020-11-15 04:08:35             🧑  作者: Mango
类型参数不能用于实例化方法内部的对象。
public static void add(Box box) {
//compiler error
//Cannot instantiate the type T
//T item = new T();
//box.add(item);
}
要实现此类功能,请使用反射。
public static void add(Box box, Class clazz)
throws InstantiationException, IllegalAccessException{
T item = clazz.newInstance(); // OK
box.add(item);
System.out.println("Item added.");
}
package com.tutorialspoint;
public class GenericsTester {
public static void main(String[] args)
throws InstantiationException, IllegalAccessException {
Box stringBox = new Box();
add(stringBox, String.class);
}
public static void add(Box box) {
//compiler error
//Cannot instantiate the type T
//T item = new T();
//box.add(item);
}
public static void add(Box box, Class clazz)
throws InstantiationException, IllegalAccessException{
T item = clazz.newInstance(); // OK
box.add(item);
System.out.println("Item added.");
}
}
class Box {
private T t;
public void add(T t) {
this.t = t;
}
public T get() {
return t;
}
}
这将产生以下结果-
Item added.