package com.tao.test;
public class User {
  private String name;
  private int id;
  public User() {
  }
  public String getName() {
    return name;
  }
  public void setName(String name) {
    this.name = name;
  }
  public int getId() {
    return id;
  }
  public void setId(int id) {
    this.id = id;
  }
}

package com.tao.test;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
public class test {
  public static void main(String[] args) throws Exception, SecurityException {
    //第一種 Constructor<?>方法
    Constructor<?> a = User.class.getDeclaredConstructor();
    a.setAccessible(true);
    User b = (User)a.newInstance();
    b.setId(1);//id字段
    b.setName("test");//name字段
    System.out.println(b.getId()+" "+b.getName());
    //第二種 Class<?>方法
    Class<?> c = Class.forName("com.tao.test.User");
    Field idF = c.getDeclaredField("id");//id字段
    idF.setAccessible(true);
    Object o = c.newInstance();
    idF.set(o, 2);
    Field nameF = c.getDeclaredField("name");//name字段
    nameF.setAccessible(true);
    Object name = c.newInstance();
    nameF.set(name, "jack");
    System.out.println(idF.get(o)+" "+nameF.get(name));
    //普通new
    User user = new User();
    user.setId(3);
    user.setName("tery");
    System.out.println(user.getId()+" "+user.getName()+" "+user.getClass());
  }
}