java - Change random operator or variable -

i have assignment in programming class. goes this, have make program takes input of user how many exercises wants do. solves simple calculations random numbers 1-10 , random operators. in end, should write how many correct , incorrect ones did get. should write elapsed time of task. did work, when assign random value operation

int operation = (int)(math.random()*3)+1;

or number , b

int = (int)(math.random()*10); int b = (int)(math.random()*10);

i same number , operator when choose second or third time task (because use loop). there way change same initialized variable or operator during program. example int a=(int)(math.random()*10) initialized in beginning example 3, , later when program loops again initialize different number, example 6. there others solutions problem? here whole code, now:

    import java.util.*;     import javax.swing.joptionpane;     public class randomchar {   public static void main(string[] args) {      char op= ' ';     int operation = (int)(math.random()*3)+1;      int = (int)(math.random()*10);     int b = (int)(math.random()*10);     string s;     int correct = 0, incorrect=0;      s = joptionpane.showinputdialog("how many exercises want?");     int num = integer.parseint(s);      long tstart = system.currenttimemillis();      while(num>0){          if(operation==1)         op='+';     else if(operation==2)         op='-';     else if(operation==3)         op='*';      string str1 = joptionpane.showinputdialog(a+" "+op+" "+b+" = ");     int num1 = integer.parseint(str1);      if(op=='+'){     if(a+b==num1)         correct++;     else         incorrect++;     }else if(op=='-'){         if(a-b==num1)             correct++;         else             incorrect++;     }else if(op=='*'){         if(a*b==num1)             correct++;                     else             incorrect++;     }     num--;     }      long tend = system.currenttimemillis();     long toverral = tend - tstart;     double elapsedseconds = toverral / 1000.0;     system.out.println("correct: "+correct);     system.out.println("incorrect: "+incorrect);     system.out.println("elapsed seconds: "+ elapsedseconds);   } 

}

simply move calculation of random numbers , operator while-loop. calculate them once.

while (num > 0) {     int operation = (int) (math.random() * 3) + 1;      int = (int) (math.random() * 10);     int b = (int) (math.random() * 10);     ... } 

so you'll have new numbers , operators in exercise.