Java 反射 调用 demo

基础类.供demo反射练习

 package fanshe;

 public class Person {
     public String name;
     private String age;
     private int p;
     public Person() {};
     public Person(String name, String age) {
         super();
         this.name = name;
         this.age = age;
     }
     private Person(String name, String age,int p) {
         super();
         this.name = name;
         this.age = age;
         this.p = p;
     }
     public String getName() {
         return name;
     }
     @Override
     public String toString() {
         return "Person [name=" + name + ", age=" + age + "]" + "p -"+ p;
     }
     public void setName(String name) {
         this.name = name;
     }
     public String getAge() {
         return age;
     }
     public void setAge(String age) {
         this.age = age;
     }
 }

反射demo类

 package fanshe;

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

 public class demo1 {

     public static void main(String[] args) {
         // TODO Auto-generated method stub
         try {
             d_3();
         } catch (Exception e) {
             // TODO: handle exception
             e.printStackTrace();
         }
     }

     private static void d_1() {
         Person p = new Person();
         Class  c = p.getClass();

     }

     private static void d_2() {
         Class  c =  Person.class;
           System.out.println(c);
     }
     private static void d_3() throws ClassNotFoundException, NoSuchMethodException, SecurityException, InstantiationException, IllegalAccessException, IllegalArgumentException, InvocationTargetException, NoSuchFieldException {
         Class  c = Class.forName("fanshe.Person");

         //--------------------------//
         Constructor con = c.getConstructor(); //获得 空参数的构造器 public
         Object o= con.newInstance(); //运行获取到的构造方法
         System.out.println(o.toString());

         //--------------------------//
         Constructor con2 = c.getConstructor(String.class,String.class); //获得带有参数的构造方法 public
         Object o2 = (Person)con2.newInstance("a","22");
         System.out.println(o2.toString());

         //--------------------------//

         Constructor con3 = c.getDeclaredConstructor(String.class,String.class,int.class); //获得带有参数的构造方法 private
         con3.setAccessible(true);
         Object o3 = (Person)con3.newInstance("a","22",14);
         System.out.println(o3.toString());

         //--------------------------//
         Object tmp_obj = c.newInstance();
         Field f_name = c.getField("name");//获得成员变量 public
         f_name.set(tmp_obj, "abc"); //设置变量
         System.out.println(tmp_obj);

         //--------------------------//
         Field f_age = c.getDeclaredField("age");//获得成员变量 public
         System.out.println(f_age);

         //--------------------------//
         Method m_getName = c.getMethod("getName"); //获得类函数无参数 public
         Object o1 = m_getName.invoke(tmp_obj); //运行getName方法.返回值 反给obj
         System.out.println(o1);

         //--------------------------//
         Method m_setName = c.getMethod("setName",String.class);
         m_setName.invoke(tmp_obj,"abcdqweqwe");
         System.out.println(tmp_obj.toString());
     }
 }

通过反射.绕开泛型

 ArrayList<String> arr = new ArrayList<String>();
 arr.add("a");
 Class carr = arr.getClass();
 Method arr_add = carr.getMethod("add",Object.class);
 arr_add.invoke(arr, 1);
 arr_add.invoke(arr, 2);
 arr_add.invoke(arr, 3);
 arr_add.invoke(arr, 4);
 System.out.println(arr);