Java反射研究（2）

接Java反射研究（1）九、調用特定方法

Method m = c1.getMethod("funcname",Class<?>...c);   //funcname表示調用方法的名稱，c表示參數的Class對象

例如：Method m = c1.getMethod("fun",String.class,int.class);    表示調用fun（String,int）;函數

Object obj = m.invoke(c1.newInstance(),"xiazdong",20);   //如果有傳回值，則invoke函數返回；

註：如果是調用靜態方法，則不需要設定對象；

Object obj = m.invoke(null,"xiazdong");

註：如果參數中有數組，比如 public static void main(String[]args);

則

Method m = c1.getMethod("main",String[].class);

m.invoke(null,(Object)new String[]{"aa","bb"});是對的；

m.invoke(null,new String[]{"aa","bb"}); 會調用 main(String,String);函數；

十、調用特定屬性

Field f = c1.getDeclaredField("name");    //返回name屬性

f.setAccessible(true);    //私人屬性可見

String name = (String)f.get(Object obj);   //返回obj對象的name屬性的值

f.set(Object obj,String n);      //設定obj對象的name屬性為n值；

十一、運算元組

int tmp[] = {1,2,3};

Class<?> c  = tmp.getClass().getComponentType();

Array.getLength(tmp);        //tmp數組的長度

c.getName();           //獲得數群組類型名稱

Array.get(Object obj,int index);      //獲得obj數組的index索引的數值

Array.set(Object obj,int index,VALUE);    //設定obj數組的index索引的數值為value；

Object obj  = Array.newInstance(c,length);          //c為數組的類型，length為數組的長度；obj為返回的數組對象；

樣本：

import java.lang.reflect.*;public class GetMethodDemo01{public static void main(String args[])throws Exception{Class<?> c1 = Class.forName("Person");Method m = c1.getMethod("sayHello");m.invoke(c1.newInstance());Method m2 = c1.getMethod("sayHello2",String.class,int.class);String str = (String)m2.invoke(c1.newInstance(),"xiazdong",123);System.out.println(str);Field nameField = c1.getDeclaredField("name");Field ageField = c1.getDeclaredField("age");nameField.setAccessible(true);ageField.setAccessible(true);Person obj = (Person)c1.newInstance();obj.setName("xzdong");obj.setAge(12);System.out.println(nameField.get(obj));System.out.println(ageField.get(obj));Method setName = c1.getMethod("setName",String.class);setName.invoke(obj,"changed");Method getName = c1.getMethod("getName");System.out.println(getName.invoke(obj));int tmp[] = {1,2,3};Class<?> c3 = tmp.getClass().getComponentType();System.out.println(c3.getName());System.out.println("第一個數："+Array.get(tmp,0));Array.set(tmp,0,5);System.out.println("第一個數："+Array.get(tmp,0));Object arr = Array.newInstance(c3,5);System.arraycopy(tmp,0,arr,0,Array.getLength(tmp));System.out.println(Array.get(arr,2));System.out.println(Array.get(arr,3));}}

import java.lang.reflect.*;interface China{public static final String NAME = "CHINA";public int AGE = 60;public void sayHello();public String sayHello2(String name,int age);}class Person implements China{private String name;private int age;public String getName(){return name;}public void setName(String name){this.name = name;}public int getAge(){return age;}public void setAge(int age){this.age = age;}public void sayHello(){System.out.println(NAME+"  "+AGE);}public String sayHello2(String name,int age){return name+" "+age;}}