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);