加减乘除

package yunsuan;
import java.util.Random;
public class yunsuan{
    public static void main(String[]args) {
        int u=1;
    Random r=new Random();
    int []p1=new int[30];
    int []p2=new int[30];
    for(int i=0;i<30;i++) {
    int a=r.nextInt(100);
    int b=r.nextInt(100);
    p1[i]=a;p2[i]=b;
    for(int j=0;j<i;j++) {
        if(p1[j]==p1[i]&&p2[j]==p2[i])
            u=0;
    }
    if(u==1) {
    int c=r.nextInt(4);
    switch(c) {
    case 0:
        System.out.println(a+"+"+b+"=");
        break;
    case 1:
        System.out.println(a+"-"+b+"=");
        break;
    case 2:
    System.out.println(a+"*"+b+"=");
    break;
    case 3:
    System.out.println(a+"+"+b+"=");
    break;
    }
    }
    }
    }
}