Java生成10个1000以内的随机数并用消息框显示数组内容然后求和输出

import javax.swing.*;
public class Sum {
  public static void main(String args[])
  {
    String output= "10个1000以内的随机数为：\n";
    int sum=0;
    int a []=new int [10];
    for(int i = 0;i<10;i++)
    {
      a[i]=(int) (Math.random()*1000);
      output += " "+a[i];
      sum += a[i];
    }
    output +="\n\n十个数的和是："+sum;
    JOptionPane.showMessageDialog(null,output,"结果",
        JOptionPane.PLAIN_MESSAGE);
  }
}