java反射实例

反射：解刨类的构造函数和创建类的对象
那么就实例来看看：

反射：解刨类的构造函数和创建类的对象
那么就实例来看看：
/*
* Person  类
*/
 package t1.no3;

public class Person {
public String name="aaa";
private int age=31;
private static int pwd=123;
public Person(){
System.out.println("Person的无参的构造函数");
}
public Person(String name){
System.out.println("Person的无有参的构造函数，name: "+name);
}
public Person(String name,int pwd,int age){
System.out.println(name+","+pwd+"，"+age);
}
private Person(int age,String name){
System.out.println(name+","+age);
}
public void say(){
System.out.println("hello");
}
public void say(String name){
System.out.println("hello name:"+name);
}
private void says(String name){
System.out.println("hello name:"+name);
}
public static void sayss(){
System.out.println("这是个静态的方法");
}
}
/*
*反射实例
*/
package t1.no3;

import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.Method;

import org.junit.Test;

public class Demo4 {
//反射public Person()构造函数
@Test
public void test1() throws Exception{
Class clazz=Class.forName("t1.no3.Person");//反射类
Constructor c=clazz.getConstructor(null);//反射构造函数
Person pp= (Person) c.newInstance(null);//创建对象
System.out.println(pp.name);
}
//反射public Person(String name)构造函数
@Test //JUnit测试
public void test2() throws Exception{
Class clazz=Class.forName("t1.no3.Person");//反射类
Constructor c=clazz.getConstructor(String.class);
Person pp=(Person) c.newInstance("XXXXXXXX");
System.out.println(pp.name);
}
//反射public Person(String name,int pwd,int age)构造函数
@Test
public void test3() throws Exception{
Class clazz=Class.forName("t1.no3.Person");//反射类
Constructor c=clazz.getConstructor(String.class,int.class,int.class);
Person pp=(Person) c.newInstance("XXXXXXXX",123456,30);
System.out.println(pp.name);
}
//反射private Person(int age,String name)构造函数
@Test
public void test4() throws Exception{
Class clazz=Class.forName("t1.no3.Person");//反射类
Constructor c=clazz.getDeclaredConstructor(int.class,String.class);//反射私有的构造函数
c.setAccessible(true);//强暴执行
Person pp=(Person) c.newInstance(30,"XXXXXXXX");//实例化对象
System.out.println(pp.name);
}
//反射public void say()方法
@Test
public void test5() throws Exception{
Person pp=new Person();
Class clazz=Class.forName("t1.no3.Person");
Method mm=clazz.getMethod("say", null);//反射方法
mm.invoke(pp, null);//执行方法
}
//反射public void say(String name)方法
@Test
public void test6() throws Exception{
Person pp=new Person();
Class clazz=Class.forName("t1.no3.Person");
Method mm=clazz.getMethod("say", String.class);
mm.invoke(pp, "XXXXXX");
}
//反射private void says(String name)方法
@Test
public void test7() throws Exception{
Person pp=new Person();
Class clazz=Class.forName("t1.no3.Person");
Method mm=clazz.getDeclaredMethod("say", String.class);
mm.setAccessible(true);
mm.invoke(pp, "XXXXXX");
}
//反射public static void sayss()方法
@Test
public void test8() throws Exception{
Person pp=new Person();
Class clazz=Class.forName("t1.no3.Person");
Method mm=clazz.getMethod("sayss", null);
mm.invoke(null, null);
}
//反射public String name="aaa";
@Test
public void test9() throws Exception{
Person pp=new Person();
Class clazz=Class.forName("t1.no3.Person");
Field fl=clazz.getField("name");//反射字段名称
System.out.println(fl.get(pp));
}
//反射private int age=31;
@Test
public void test10() throws Exception{
Person pp=new Person();
Class clazz=Class.forName("t1.no3.Person");
Field fl=clazz.getDeclaredField("age");//反射私有字段名称
fl.setAccessible(true);//强制执行
System.out.println(fl.get(pp));
}
//反射private static int pwd=123;
@Test
public void test11() throws Exception{
//Person pp=new Person();
Class clazz=Class.forName("t1.no3.Person");
Field fl=clazz.getDeclaredField("pwd");
fl.setAccessible(true);//强制执行
System.out.println(fl.get(null));//static静态的字段，这里可以field.get(null)
}
}