Java- Sorting int array

Question

I'm trying to use this method to sort an integer array in ascending order. But my for loop runs through it only once.

public void sortArray()
{
   boolean sorted = false;

   while(sorted == false)
   {
       int temp;
       for(int i = 0; i < inArray.length - 1; i++)
       {
          if(inArray[i] > inArray[i + 1])
          {
             temp = inArray[i];
             inArray[i] = inArray[i + 1];
             anArray[i + 1] = temp;
          }
       }
       sorted = true;
   }
}

I know it has to do with how I'm handling that boolean flag, but I'm not sure how to go about fixing it. Any suggestions would be appreciated. Thanks in advance.

= is assignment, == is equality. This is why you should always just write while (!sorted) instead. It protects you from this sort of typo. — azurefrog
– azurefrog, Commented Nov 1, 2016 at 22:22
"But my for loop runs through it only once." No, your current while loop doesn't ever execute the loop body at all, because of what azurefrog points out above. If you fix that, it will only ever run once, because you set sorted = true unconditionally at the end of the loop. — T.J. Crowder
– T.J. Crowder, Commented Nov 1, 2016 at 22:23
@azurefrog Thank you for pointing that out, I actually have it as == in my actual code but messed it up while typing it on here. — Bluasul
– Bluasul, Commented Nov 1, 2016 at 22:25
@Bluasul: Why would you retype it? That's what copy and paste are for. — T.J. Crowder
– T.J. Crowder, Commented Nov 1, 2016 at 22:28
@T.J.Crowder I felt that by typing it again I would be sort of reviewing it more carefully and maybe find a solution before posting the question. It turned out to be the opposite since I ended up messing it up further, but oh well. — Bluasul
– Bluasul, Commented Nov 1, 2016 at 22:33

T.J. Crowder · Accepted Answer · 2016-11-01 22:26:55Z

There are multiple issues here:

while (sorted = false) sets sorted to false and then tests the resulting value false, meaning that you never enter the loop body at all (not once as per your question).
If you fix that, your code will only run the while loop body once (thus leaving the array not sorted yet), because you have sorted = true as an unconditional statement at the end of the loop body.

You need to have a flag that assumes the array is sorted, and then is cleared if you find evidence it wasn't, something like:

public void sortArray()
{
   boolean sorted;

   do
   {
       sorted = true;  // Assume it's sorted
       int temp;
       for(int i = 0; i < inArray.length - 1; i++)
       {
          if(inArray[i] > inArray[i + 1])
          {
             temp = inArray[i];
             inArray[i] = inArray[i + 1];
             anArray[i + 1] = temp;
             sorted = false; // We changed something, so assume we need to do another pass
          }
       }
   }
   while (!sorted);
}

Side note: This is just a style thing, but it's generally best to scope variables as narrowly as possible. There's no need for temp to be outside the for loop or even outside the if block, move it inside the if block

public void sortArray()
{
   boolean sorted;

   do
   {
       sorted = true;  // Assume it's sorted
       for(int i = 0; i < inArray.length - 1; i++)
       {
          if(inArray[i] > inArray[i + 1])
          {
             int temp = inArray[i];
             inArray[i] = inArray[i + 1];
             anArray[i + 1] = temp;
             sorted = false; // We changed something, so assume we need to do another pass
          }
       }
   }
   while (!sorted);
}

score 3 · Accepted Answer · 2016-11-02 09:18:33Z

You currently are setting your sorted to true allways at the end of the loop. While of course it should only be true if actually no reshuffling took place.

One way to archieve this would be to set sorted to true at the start of your while loop, and set it to false when you detect that the array is not yet sorted and you do the switching of elements:

public void sortArray()
{
   boolean sorted = false;

   while(!sorted)
   {
       sorted = true;
       int temp;
       for(int i = 0; i < inArray.length - 1; i++)
       {
          if(inArray[i] > inArray[i + 1])
          {
             sorted = false; // array is not yet sorted
             temp = inArray[i];
             inArray[i] = inArray[i + 1];
             anArray[i + 1] = temp;
          }
       }

   }
}

Борис Ёлкин · Accepted Answer · 2018-09-21 21:18:25Z

My method which contains no java collections

public class Main {
public static void main(String[] args) {
    /** By Boris Elkin 21.09.2018 в 22.59 MSK You can input any digits, sorting was made without collections on purpose.
     **/

    int[] a1=new int[]{1,245623,3,3,3,3454,6,8123,234,123123,797897};
    int[] a2=new int[]{234234, 33,4234,5,646456,9,78};
    int[] a3;
    a3= collide(a1, a2);
    a3=sort(a3);
    checkArray(a3);
}
public static int[] collide(int[]a, int[]b){
    int breakpoint=0;
    int size=a.length+b.length;
    int[]c=new int[size];
    for(int i=0;i<a.length;i++){
        c[i]=a[i];
        breakpoint=i;
    }
    for(int i=breakpoint+1,j=0;j<b.length;i++, j++){
        c[i]=b[j];
    }
    return c;
}
public static int[] sort(int a[]){
    boolean engine=true;
    while(engine) {
        for(int i=0;i<a.length;i++){
            int temp, temp2;
            if ((i + 1 < a.length) && (a[i] > a[i + 1])) {
                temp = a[i];
                temp2 = a[i + 1];
                a[i + 1] = temp;
                a[i] = temp2;
            }
        }
        if(checkThreadLogistic(a)){
            engine=false;
        }
    }
    return a;
}

private static boolean checkThreadLogistic(int[] a) {
    return checkCertainElement(a);
}

private static boolean checkCertainElement(int[] a) {
    for(int i=0;i<a.length;i++){
        if(i>1){
            for(int j=a.length;j>i;j--){
                if(j<a.length) if(a[i]>a[j])return false;
            }
        }
    }
    return true;
}

public static void checkArray(int[]array){
    for (int anArray : array) {
        System.out.println(anArray + "");
    }
}
}

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