Compare two arrays to get the missing array and new array in java

Question

I have an array which shows the cities selected in database as cities=["1","3"] where 1 is Bombay and 3 is bangalore

Now while editing the user deselects Bombay and selects chennai, The new array is ["2","3"]

HTML:

<select name="cities">

<option value="1">Bombay</option>
<option value="2">Chennai</option>
<option value="3">Bangalore</option>
<option value="4">Delhi</option>
<option value="5">Calcutta</option>
</select>

How to get an array which contains the missing values(1) and an array for newly selected (2) so that when compared with selected array, if it is missing should update else should insert in database

yes should the get missing in one array and newly selected in one array and later if missing array then should update in database else insert — user3841558, Nov 19 '14 at 06:48

score 3 · Answer 1 · edited May 23 '17 at 12:16

You can use guava libraries for getting the difference between the sets. What you can do is convert bothe the arrays to Set

new HashSet(Arrays.asList(array)); And similalarly for the sencond array as well

Then pass the Sets to guava difference method

public static Sets.SetView difference(Set set1, Set set2)

.If you don't want to use any 3rd party libraries, You can check out this question question

score 0 · Answer 2 · answered Nov 19 '14 at 07:32

0

public class Main {

public static void main(String[] args) {
  final String[] arr1 = {"1", "3"};
  final String[] arr2 = {"2", "3"};
  List<String> missing = new ArrayList<String>(); // the missing vals
  List<String> have = new ArrayList<String>();    // the common vals
  List<String> newV = new ArrayList<String>();    // the new entries

  Set<String> aSet = new HashSet<String>(Arrays.asList(arr1));
  Set<String> bSet = new HashSet<String>(Arrays.asList(arr2));

  for (String s : aSet) {
    if (bSet.contains(s)) {
      have.add(s);
    } else {
      missing.add(s);
    }
  }

  for (String s : bSet) {
    if (!aSet.contains(s)) {
      newV.add(s);
    }
  }
}
}

answered Nov 19 '14 at 07:32

gashu

484
6
17

can you tell me only using list instead of set – user3841558 Nov 19 '14 at 07:40
kindly help me doing using list alone – user3841558 Nov 19 '14 at 07:41
Just replace `Set aSet = new HashSet(Arrays.asList(arr1)); ` with `List aSet = Arrays.asList(arr1);` but this won't weed out the duplicates. – gashu Nov 19 '14 at 09:40

Compare two arrays to get the missing array and new array in java

2 Answers2