（1）题目避免重复； （2）可定制（数量/打印方式）；

代码实现

import java.util.ArrayList;
import java.util.Random;
import java.util.Scanner;

public class test_02 {
    public static void main(String[] args) {
        Random rm=new Random();
        Scanner sc=new Scanner(System.in);
        int num=sc.nextInt();
        //int [][]arr=new int[num][num];
        ArrayList<String> arr=new ArrayList<String>();
        for (int i=0;i<num;i++){
            int number_3=rm.nextInt(4)+1;//1到4
            int number_1= rm.nextInt(100)+1;
            int number_2=rm.nextInt(100)+1;
//                if (number_3==1){
//                    StringBuilder sb=new StringBuilder();
//                    sb.append(number_1).append("+").append(number_2);
//                    for (int j=0;j<arr.size();j++){
//                        if (arr.get(i).equals(sb.toString())){
//                            number_1= rm.nextInt(100)+1;
//                            number_2=rm.nextInt(100)+1;
//                            break;
//                        }
//                    }
//                }

            if(number_3==1){
                System.out.println(number_1+"+"+number_2);
                StringBuilder sb=new StringBuilder();
                sb.append(number_1).append("+").append(number_2);
                arr.add(sb.toString());
            }else if(number_3==2){
                System.out.println(number_1+"-"+number_2);
                StringBuilder sb=new StringBuilder();
                sb.append(number_1).append("-").append(number_2);
                arr.add(sb.toString());
            }else if (number_3==3){
                System.out.println(number_1+"*"+number_2);
                StringBuilder sb=new StringBuilder();
                sb.append(number_1).append("*").append(number_2);
                arr.add(sb.toString());
            }else if(number_3==4){
                System.out.println(number_1+"/"+number_2);
                StringBuilder sb=new StringBuilder();
                sb.append(number_1).append("*").append(number_2);
                arr.add(sb.toString());
            }
        }
    }
}