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
– user3841558, Commented Nov 19, 2014 at 6:48

Community · Accepted Answer · 2017-05-23 12:16:42Z

3

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

edited May 23, 2017 at 12:16

CommunityBot

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answered Nov 19, 2014 at 7:11

FatherMathew

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Comments

gashu · Accepted Answer · 2014-11-19 07:32:12Z

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, 2014 at 7:32

gashu

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3 Comments

user3841558 Over a year ago

can you tell me only using list instead of set

user3841558 Over a year ago

kindly help me doing using list alone

gashu Over a year ago

Just replace Set<String> aSet = new HashSet<String>(Arrays.asList(arr1)); with List<String> aSet = Arrays.asList(arr1); but this won't weed out the duplicates.

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