CODEWITHSUNDEEP
javaarraysbooleancompare
Andrew DeWitt
Andrew DeWitt

Reputation: 57

How to compare arrays without using .equals and with a false boolean

I am having to compare arrays without using the .equals method and currently the program runs correctly except when I have two variables such as 

int[] y = {8,8,8};
int[] z = {8,8,9};

My program says this is true when it should say it is false. The following is my CompareArrays code:

if (arrayOne.length == arrayTwo.length) {
   for (int i = 0; i < arrayOne.length; i++) {
      if (arrayOne[i] == arrayTwo[i]) {
         return true;
      }
   }
}

return areEqual;

I have to use the boolean areEqual = false and return it at the end.

Upvotes: 0

Views: 1241

Answers (3)

Andy Turner
Andy Turner

Reputation: 140544

You are returning true as soon as you find a matching pair of elements, and never updating areEqual. You need to keep going until you find a pair of elements which aren't equal, or reach the end of the array.

Instead, use the areEqual variable to tell you if you have found something - anything - which makes them unequal. Once you have found something to make them unequal, you don't need to check any more:

boolean areEqual = false;  // Redundant assignment; but meh, if you've got to use this...
areEqual = arrayOne.length == arrayTwo.length;
for (int i = 0; areEqual && i < arrayOne.length; ++i) {
  areEqual = arrayOne[i] == arrayTwo[i];
}
return areEqual;

Upvotes: 0

QuickSort
QuickSort

Reputation: 664

@Mayhem 's answer is correct. I just want you to show you a more cleaner way (by removing the if nesting):

if (arrayOne.length != arrayTwo.length) {
  return false;
}

for (int i = 0; i < arrayOne.length; i ++) {
  if (arrayOne [ i ] != arrayTwo [ i ] ) {
    return false; 
  }
}
return true;

Upvotes: 0

fasaas
fasaas

Reputation: 702

Instead of immediately returning when they are equal, check for inequalities and if there's one, then return false. If the for loop finishes without returning, then you can safely return true. 

if (arrayOne.length == arrayTwo.length) {

    for (int i = 0; i < arrayOne.length; i ++) {

        if (arrayOne [ i ] != arrayTwo [ i ] ) {

            return false; 
        }

    }

    return true;

}
return false;

Upvotes: 3

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