问用JAVA打印10个随机问题

EN

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

public class HelloWorld{
  public static void main(String [] args){
    Scanner keyboard = new Scanner(System.in);
    int sum = 0;
    int userAnswer ;
    int check ;

    // Random number generating
    // Ask the user for input 10 times
    for (int i = 0; i < 10; i++) {
      Random generator = new Random();

      int N1 = generator.nextInt(100);
      int N2 = generator.nextInt(N1);
      int N3 = generator.nextInt(2);

      // if N3 is even use plus, if odd use minus
      Boolean plus = N3 % 2 == 0;

      // Set a string to either "+" or "-" depending on the value of plus
      String plusMinus = plus? "+" : "-";

      System.out.println(" What is the answer to " + N1 + plusMinus + N2 + " = " );
      userAnswer = new Scanner(System.in).nextInt();

      // Display if its correct or not
      // Set the answer depending on the value of plus.
      check = plus? N1 + N2 : N1 - N2;

      if(userAnswer == check){
        System.out.println("You are correct!");
      }
      else{
        System.out.println(" Sorry, the correct answer is : " + check);
      }
    }

  }
}

Random generator = new Random();
int var1 = generator.nextInt(100);
int var2 = generator.nextInt(100);
int choice = generator.nextInt(3);

switch (choice){
    case 0:
         System.out.println(var1 + " + " + var2);
         break;
    case 1:
         System.out.println(var1 + " - " + var2);
         break;
    case 2:
         System.out.println(var1 + " * " + var2);
         break;
    case 3:
         System.out.println(var1 + " / " + var2);
         break;
 }