求一个利用java反射的例子

[kent4j]

不太理解反射的作用

[loveofmylife]

import java.lang.reflect.*;
public class ReflectionTest {
	public static void main(String[] args) {
		Class c=null;
		try {
			c=Class.forName("java.lang.String");
			System.out.println("package "+c.getPackage().getName()+";");
			System.out.print(Modifier.toString(c.getModifiers())+" ");
			System.out.print("class "+c.getSimpleName()+" ");
			if (c.getSuperclass()!=Object.class) {
				System.out.print("extends " + c.getSuperclass().getSimpleName());
			}
			Class[] inters=c.getInterfaces();
			if(inters.length>0){
				System.out.print("implements ");
				for(int i=0;i<inters.length;i++){
					System.out.print(inters[i].getSimpleName());
					if(i<inters.length-1){
						System.out.print(",");
					}
				}
			}
			System.out.println("{");
			printFields(c);
			printMethods(c);
			System.out.println("}");
		} catch (ClassNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
			
	}
	public static void printFields(Class c){
		Field[] field=c.getDeclaredFields();
		if(field.length>0){
			for(int i=0;i<field.length;i++){
				System.out.println(Modifier.toString(field[i].getModifiers())+" "+field[i].getType().getSimpleName()+" "+field[i].getName()+";");
			}
		}
	}
	public static void printMethods(Class c){
		Method[] method=c.getDeclaredMethods();
		if(method.length>0){
			for(int i=0;i<method.length;i++){
				Class[] parameter=method[i].getParameterTypes();
				System.out.print(Modifier.toString(method[i].getModifiers())+" "+method[i].getReturnType().getSimpleName()+" "+method[i].getName()+"(");
				for(int j=0;j<parameter.length;j++){
					System.out.print(parameter[j].getSimpleName()+" args");
					if(j!=parameter.length-1){
						System.out.print(",");
					}
				}
				System.out.print(") ");
				Class exception[]=method[i].getExceptionTypes();
				
				if (exception.length>0) {
					System.out.print("throws ");
					for (int j = 0; j < exception.length; j++) {
						System.out.print(exception[j].getSimpleName());
					}
				}
				System.out.println("{");
				System.out.println("\t... ...");
				System.out.println("}");
			}
			
		}
	}

}

打印String类结构，可以参考一下。

[rookie001]

我也贴个，以前写的一个小作业，利用java提供的反射机制得到用户在程序运行时输入的类名，输出该类所在继承体系中的所有类中定义的方法，所有方法需按字母排序。
import java.lang.reflect.*;
import java.util.*;
import java.io.*;
/**
* PrintMethods class
* 本类利用java的反射机制，获取某个类继承体系的所有方法，按字母排序显示
* printAll,printMethods方法均可以静态调用
*/
public class PrintMethods {
//打印某个类的整个体系的所有方法
public static void printAll(String className){
try{
Class c = Class.forName(className);
System.out.println("******************Methods*******************\n");
while(c!=null){
printMethods(c.getName());
c = c.getSuperclass(); //得到本类的超类
}
System.out.println("\n");
}catch(ClassNotFoundException e){
System.out.println(e.toString());
}
}
/**
* 打印某类的所有方法
* 利用反射机制
* @param className类名
*/
public static void printMethods(String className){
try{
Class classTemp = Class.forName(className);
Method [] method = classTemp.getMethods(); //得到类的方法
Method methodTemp = null;
TreeMap<String,Method> tm = new TreeMap<String,Method>(); //TreeMap：方法名为key，方法为value
for(int i=0;i<method.length;i++){
tm.put(method[i].getName(), method[i]); //TreeMap 的初始化，再迭代打印即为字母排序
}
System.out.println("\n*********************************************************************");
System.out.print("\nMethods of the class "+className+":");
Iterator<Method> e = tm.values().iterator();
while(e.hasNext()){
methodTemp = e.next();
int mods = methodTemp.getModifiers();
String strm = Modifier.toString(mods); //方法修饰符
System.out.print(" \n"+strm);
System.out.print(" "+methodTemp.getReturnType().getSimpleName()); //返回类型
System.out.print(" "+methodTemp.getName()+"("); //方法名
Class [] p = methodTemp.getParameterTypes(); //打印参数
for(int k=0;k<p.length;k++){

System.out.print(p[k].getSimpleName());
if(p.length>k+1){
System.out.print(",");
}
}
System.out.print(")");
Class []ep = methodTemp.getExceptionTypes(); //打印抛出的异常
if(ep.length!=0){
System.out.print("throws ");
for(int j=0;j<ep.length;j++){
System.out.print(ep[j].getSimpleName());
if(ep.length>j+1)System.out.print(",");
}
}

}
}catch (ClassNotFoundException e){
System.out.println(e.toString());
}
}
//测试
public static void main(String[] args) throws IOException{
// TODO Auto-generated method stub
String className;
BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
while(true){
System.out.println("Please input the name of the class,'quit' to exit:");
className = br.readLine();
if(className.equals("quit")){
System.exit(0);
}
PrintMethods.printAll(className);
}

}

}

[amdgaming]

学习，看看

[dyccsxg]

import java.lang.reflect.Method;

public class Test{    
    
    public static void main(String [] args){     
        try{
            //实例化类
            People obj=(People)Class.forName("People").newInstance();            
            
            Method method=null;
            //调用setName(String name)方法
            method=obj.getClass().getMethod("setName",new Class[]{String.class});
            method.invoke(obj,new Object[]{"princess"});
            //调用getName()方法
            method=obj.getClass().getMethod("getName");
            String result=(String)method.invoke(obj);
            
            System.out.println("result is : "+result);
        }catch(Exception e){
        }
        System.out.println("...ok...");    
    }    
}
class People {
    private String name;
    
    public People(){
        name="no name";
    }
    public People(String name){
        this.name=name;
    }
    //--get set methods--
    public void setName(String name){
        this.name=name;
    }
    public String getName(){
        return this.name;
    }    
}