使用eclipse启动Tomcat后没有打印出随机验证码code

package com.imooc.code;

import java.util.Random;

import javax.servlet.http.HttpServletResponse;

/*

 * 验证码工具类

 */

public class CaptcahCode {

/*

* 验证生成的方法

* @param response

* @return

*/

public static String drawImage(HttpServletResponse response) {

//1:定义以字符串的拼接的StringBuilder

StringBuilder builder=new StringBuilder();

//准备产生4个字符串的随机数

for(int i=0;i<4;i++) {

builder.append(randomChar());

}

String code=builder.toString();

System.out.print("==================================");

System.out.print("code:"+code);

System.out.print("==================================");

return null;

}

private static char randomChar() {

//1：定义验证需要的字母和数字

String string ="QWERTYUIOPASDFGHJKLZXCVBNM0123456789";

//2:定义随机对象

Random random=new Random();

return string.charAt(random.nextInt(string.length()));

}

public static void main (String[] args) {

CaptcahCode.drawImage(null);

}

}