泛型對象可以實例化嗎？

不可以，T t=new T()是不可以的，編譯器會報錯。由于泛型擦除，編譯器在編譯時無法確定泛型所對應的真實類型

解決方法

使用反射新建實例

Type superclass = getClass().getGenericSuperclass();ParameterizedType parameterizedType = null;if (superclass instanceof ParameterizedType) { parameterizedType = (ParameterizedType) superclass; Type[] typeArray = parameterizedType.getActualTypeArguments(); if (typeArray != null && typeArray.length > 0) { clazz = (Class<T>) typeArray[0]; }}

執行結果

控制臺輸出

完整代碼

package com.learn.genericinstance;import java.lang.reflect.ParameterizedType;import java.lang.reflect.Type;public class GenericInstanceLearn { public static void main(String[] args) throws InstantiationException, IllegalAccessException { UserDao userDao = new UserDao(); System.out.println(userDao.toString()); }}class Dao<T> { public Class<T> clazz; public T user; public Dao() throws IllegalAccessException, InstantiationException { Type superclass = getClass().getGenericSuperclass(); ParameterizedType parameterizedType = null; if (superclass instanceof ParameterizedType) { parameterizedType = (ParameterizedType) superclass; Type[] typeArray = parameterizedType.getActualTypeArguments(); if (typeArray != null && typeArray.length > 0) {clazz = (Class<T>) typeArray[0];user= clazz.newInstance(); } } } @Override public String toString() { return 'Dao{' +'user=' + user.toString() +’}’; }}class UserDao extends Dao<User> { public UserDao() throws IllegalAccessException, InstantiationException { } @Override public String toString() { return super.toString(); }}class User { String name; public User() { this.name = 'default name'; } @Override public String toString() { return 'User{' +'name=’' + name + ’’’ +’}’; }}

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