java反射使用及性能比较

环境准备

package com.lilei.pack09;

public class Logger {

    
    public void show(){
        System.out.println("hello world");
    }
    
    public int cal(int a,int b){
        return a + b;
    }
    
    public String multi(String... args){
        
        return args.length+";";
    }
    
    
}

使用反射

package com.lilei.pack09;

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

public class app1 {

    public static void main(String[] args) throws ClassNotFoundException, NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {
        

        Class c = Class.forName("com.lilei.pack09.Logger");
        
        
        
        Method[] ms = c.getMethods();
        
        Method m_show = c.getMethod("show", null);
        
        m_show.invoke(new Logger(), null);
        
        Method m_cal = c.getMethod("cal", new Class[]{int.class,int.class});
        
        Object result = m_cal.invoke(new Logger(), 233,2233);
        
        new Logger().multi("v","dd","ds");
        
        System.out.println(result);
        
        Method m_multi = c.getMethod("multi", new Class[]{String[].class});
        
        result = m_multi.invoke(new Logger(), new Object[]{new String[]{"v","dd","ds"}});
        
        System.out.println(result);
    }

}

性能比较

常规创建对象调用方法和通过反射进行调用方法

package com.lilei.pack09;

import java.util.Date;

public class app2 {

    public static void main(String[] args) {

        Logger logger = new Logger();

        
        int result = 0;

        System.out.println(new Date());
        for (int i = 0; i < 2000000000; i++){
            result += logger.cal(i,i);
        }

        System.out.println(result);
        System.out.println(new Date());
    }

}

消耗时间：

package com.lilei.pack09;

import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.Date;

public class app3 {

    public static void main(String[] args) throws NoSuchMethodException, SecurityException, IllegalAccessException, IllegalArgumentException, InvocationTargetException {

        Logger logger = new Logger();
        
        Method m = logger.getClass().getMethod("cal", new Class[]{int.class,int.class});

        
        int result = 0;

        System.out.println(new Date());
        for (int i = 0; i < 2000000000; i++){
            Integer in = (Integer)m.invoke(logger, i,i);
            result += in.intValue();
        }

        System.out.println(result);
        System.out.println(new Date());
    }

}

消耗时间：

通过使用反射消耗的时间是通过对象调用方法的40-50倍