Java中反射的三种常用方式
Java中反射的三种常用方式
package com.xiaohao.test;
public class Test{
public static void main(String[] args) throws ClassNotFoundException, InstantiationException, IllegalAccessException {
// Class<?> clazz=Class.forName("com.xiaohao.test.User"); //1方法一
// User user=(User) clazz.newInstance();
// User user=User.class.newInstance(); //2 方法二
User user2=new User(); //3 方法三
User user=user2.getClass().newInstance();
user.setId(10);
user.setUserName("小浩");
user.setPassword("123456");
System.out.println(user);
}
}
package com.xiaohao.test;
import java.util.ArrayList;
import java.util.List;
public class User {
private Integer id;
private String userName;
private String password;
List<String> books=new ArrayList<String>();
public Integer getId() {
return id;
}
public void setId(Integer id) {
this.id = id;
}
public String getUserName() {
return userName;
}
public void setUserName(String userName) {
this.userName = userName;
}
public String getPassword() {
return password;
}
public void setPassword(String password) {
this.password = password;
}
public User(String userName, String password) {
super();
this.userName = userName;
this.password = password;
}
public User() {
super();
}
public List<String> getBooks() {
return books;
}
public void setBooks(List<String> books) {
this.books = books;
}
@Override
public String toString(){
return this.id+" "+this.userName+" "+this.password+" ";
}
}
package com.xiaohao.test;
import java.lang.reflect.Array;
import java.lang.reflect.Field;
import java.lang.reflect.Method;
public class Test{
public static void main(String[] args) throws Exception {
// Class<?> clazz=Class.forName("com.xiaohao.test.User"); //1方法一
// User user=(User) clazz.newInstance();
// User user=User.class.newInstance(); //2 方法二
User user2=new User(); //3 方法三
User user=user2.getClass().newInstance();
System.out.println("user2对象的值为:"+user2);
System.out.println("类的名字为:"+user2.getClass().getName());
// Field field=user2.getClass().getDeclaredField("number");
// Field field=User.class.getDeclaredField("number");
Field field=Class.forName("com.xiaohao.test.User").getDeclaredField("number");
field.setAccessible(true);
field.set(user2,"1000");
System.out.println("user2对象的值为:"+user2);
Method method=User.class.getDeclaredMethod("setUserName",String.class);
method.invoke(user2,"小浩爷爷");
System.out.println("user2对象的值为:"+user2);
Class<?> component=Class.forName("com.xiaohao.test.User").getDeclaredField("address").get(user2).getClass().getComponentType();
User.class.getDeclaredField("address").setAccessible(true);
int length=((String[])User.class.getDeclaredField("address").get(user2)).length;
System.out.println("user2中原始的数组的长度为:"+length);
Object [] array=(Object[]) Array.newInstance(component, length+75);
System.out.println("user2中修改后的数组的长度为:"+array.length);
user.setId(10);
user.setUserName("小浩");
user.setPassword("123456");
System.out.println(user);
}
}
package com.jd.singleton;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
/**
*
*
* Created by zhanghao10 on 2016/5/9.
*/
public class Reflect {
/**
* 测试反射生成对应的方法
*/
public static void main (String args[]) throws ClassNotFoundException, IllegalAccessException, InstantiationException, InvocationTargetException, NoSuchFieldException, NoSuchMethodException {
// Class<?> clazz= Class.forName("com.jd.singleton.User");
// User user= (User) clazz.newInstance();
// User user2= (User) clazz.newInstance();
// System.out.println(user==user2);
// user.setName("Hello World");
// System.out.println(user.equals(user2));
// System.out.println(user.getName());
// System.out.println(user2.getName());
// Class<User> clazz2=User.class;
// User user=clazz2.newInstance();
// user.setName("Hello World");
// System.out.println(user.getName());
// User user=new User();
// User user1=user.getClass().newInstance();
// user1.setName("Hello World");
// System.out.println(user.getName());
// Integer n1 = new Integer(47);
// Integer n2 = new Integer(47);
//
// System.out.println(n1 == n2);
// System.out.println(n1.equals(n2));
// Class<?> clazz= Class.forName("com.jd.singleton.User");
// Constructor<?>[] cons=clazz.getConstructors();
// System.out.println(cons.length);
// Class<?> clazz=Class.forName("com.jd.singleton.User");
// Constructor<?> [] cons= clazz.getDeclaredConstructors();
// cons[0].setAccessible(true);//对于私有方法，需要设置可见性为false
// User user= (User) cons[0].newInstance();
// user.setName("123456");
// System.out.println(user.getName());
// Class<?> clazz=Class.forName("com.jd.singleton.User");
// Constructor<?> [] cons= clazz.getDeclaredConstructors();
// cons[0].setAccessible(true);//对于私有方法，需要设置可见性为false
// User user= (User) cons[0].newInstance();
// user.setName("123456");
// System.out.println(user.getName());
// Class<?> clazz=Class.forName("com.jd.singleton.User");
// User user= (User) clazz.newInstance();
// Field filedName=clazz.getDeclaredField("name");
// filedName.setAccessible(true);
// filedName.set(user,"我是小浩也");
// System.out.println(user.getName());
// Class<?> clazz=Class.forName("com.jd.singleton.User");
// User user= (User) clazz.newInstance();
// Method method=clazz.getDeclaredMethod("setName",String.class);
// method.invoke(user,"天下太平");
// System.out.println(user.getName());
Class<?> clazz=Class.forName("com.jd.singleton.User");
User user= (User) clazz.newInstance();
Method method=clazz.getDeclaredMethod("setName",String.class,int.class);
method.invoke(user,"天下太平",123456);
System.out.println(user.getValue());
}
}
package com.jd.singleton;
/**
* Created by zhanghao10 on 2016/5/9.
*/
public class User {
// private User(){}
private String name;//用户名称
private int value;
public String getName() {
return name;
}
public int getValue(){
return value;
}
public void setName(String name,int value) {
this.name = name;
this.value=value;
}
@Override
public int hashCode() {
return (int) (Math.random()*100);
// return super.hashCode();
}
@Override
public boolean equals(Object obj) {
return true;
// return super.equals(obj);
}
}
