Question

My boolean expression becomes false in the middle of my loop. What kind of loop should I use?
I keep reading through loop tutorials and each one mentions that a while loop cannot do this. I’ve tried combining a for loop and an if statement and that doesn’t work either. Sorry for the simple question.

    }
     for(int k = 0;k < collb.length; k++){
        //what was used after first calculation
           grosssum += col4[k]*mix[k];
             one=sum1 - grosssum;


    }
   for(int n = 0;n < collb.length; n++)
    if(one < -need[n] && col4[n] >0){
   col5[n]=col4[n]-inc[n] + arrayspecificpounds[n];
    net += col5[n]*mix[n];
    sum = sum1-net;
 }   //net is the sum of what was used * mix
     //sum1 is what we started with
   else{
     if(one > need[n] && col4[n] >0){
    col5[n]=col4[n]-inc[n] + arrayspecificpounds[n];
    net += col5[n]*mix[n];
    sum = sum1-net;

    }
    else col5[n] = col4[n] +  arrayspecificpounds[n];
    sum = sum1 - net;
   }
   for(int p = 0;p< collb.length; p++){
       if(sum < -need[p] && col5[p] >0){
           col6[p]=col5[p]-inc[p] + arrayspecificpounds[p];
       net2 += col6[p]*mix[p];
       sum2 = sum1 - net2;
       }
     else{
           if(sum > need[p] && col5[p] >0){
               col6[p]=col5[p]+inc[p] + arrayspecificpounds[p];
      net2 += col6[p]*mix[p];
    sum2 = sum1 - net2;
           }
    else col6[p] = col5[p] + arrayspecificpounds[p];
    net2 += col6[p]*mix[p];
    sum2 = sum1 - net2;
   }
    }


        for(int q =0;q< collb.length; q++){
           if(sum2 < -need[q] && col6[q] >0){
               colr[q]=col6[q] - inc[q] +arrayspecificpounds[q];
           }
             else{
               if(sum2 > need[q] && col6[q]>0){
                   colr[q]=col6[q] +inc[q] + arrayspecificpounds[q];
               }
       else colr[q] = col6[q] + arrayspecificpounds[q];
           }    

In this example sum2’s value changes as array col6 is incremented but in the middle of the array the inequalities change. How would I implement a break to stop once sum2 changes?

Answer 1

Here is a simple example of how you can stop a while loop when a boolean value you’re monitoring changes it’s value from false to true:

boolean done = false;
int count = 0;

// while not done, continue looping
while(!done) {
    // do stuff
    count++;
    if(count > 7) {
        done = true;
    }
}

The same technique can actually be used inside a for loop as well:

boolean done = false;
for(int i = 0; i < 1000 && !done; i++) {
    // do stuff

    if(i > 7) {
        done = true;
    }
}

This is a bit unorthodox, but it demonstrates how the 2nd parameter in your for loop can be used to monitor a boolean condition that may or may not be related to the actual value of the int i value.