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How to change only the first occurrence of an object in an ArrayList, ignoring subsequent duplicates, in Java


How to change only the first occurrence of an object in an ArrayList, ignoring subsequent duplicates, in Java

By : Mohammed Zomam
Date : November 20 2020, 03:01 PM
With these it helps I wish to take an array of integers and check it against two numbers, the first of which is the number in the array that I want to replace and the second number is the number that I wish to replace the first number by. I have managed to write the code to do this both destructively and constructively, but I want to only change the first occurrence of the number I first enter to the second number, not all the entries. , Add a break statement inside your if:
code :
if (list.get(i) == numberCompare) {
    list.set(i, numberReplace);
    break;
}


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Java-I have an ArrayList contains objects, after one occurrence I want the object is added to another list

Java-I have an ArrayList contains objects, after one occurrence I want the object is added to another list


By : HiFiHair
Date : March 29 2020, 07:55 AM
hope this fix your issue i have this ArrayList ID that contains objects:
code :
import java.util.HashSet;

public class Test {

    private static final HashSet<Integer> onetimevisit = new HashSet<Integer>();
    private static final HashSet<Integer> alreadyVisited = new HashSet<Integer>();

    public static void addVisitor(Integer visitorId){
        if(onetimevisit.contains(visitorId))
            alreadyVisited.add(visitorId);
        else
            onetimevisit.add(visitorId);
    }
}
Remove Duplicates from ArrayList<ArrayList<String>> Object

Remove Duplicates from ArrayList<ArrayList<String>> Object


By : Adamson
Date : March 29 2020, 07:55 AM
will be helpful for those in need What aioobe said, using a set, except you will put it in a loop since you have a two demisional array:
code :
Set<String> set = new LinkedHashSet<String>();
for (ArrayList<String> list:yourList) {
    set.addAll (list);
}
ArrayList<String> uniqueList = new ArrayList<String>(set);
Find duplicates in an ArrayList and set the duplicates to new ArrayList dynamically using Java

Find duplicates in an ArrayList and set the duplicates to new ArrayList dynamically using Java


By : Judy
Date : March 29 2020, 07:55 AM
I think the issue was by ths following , The best way is to use a Map. Check is the map contains a key of the String. If it doesn't create a new List and add it to the map. If it does, then just add the String the list already in the map.
code :
public static Map<String, List<String>> getMap(List<String> list) {
    Map<String, List<String>> map = new HashMap<>();

    for (String s: list) {
        if (!map.containsKey(s)) {
            List<String> mapList = new ArrayList<>();
            mapList.add(s);
            map.put(s, mapList);
        } else {
            ((List<String>)map.get(s)).add(s);
        }
    } 
    return map;
}
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class TestLIst {

    public static void main(String[] args) {
        List<String> list = new ArrayList<String>();
        list.add("A");
        list.add("B");
        list.add("A");
        list.add("B");
        list.add("C");
        list.add("D");

        Map<String, List<String>> map = getMap(list);
        printMapAsLists(map);
    }

    public static Map<String, List<String>> getMap(List<String> list) {
        Map<String, List<String>> map = new HashMap<>();

        for (String s: list) {
            if (!map.containsKey(s)) {
                List<String> mapList = new ArrayList<>();
                mapList.add(s);
                map.put(s, mapList);
            } else {
                ((List<String>)map.get(s)).add(s);
            }
        } 
        return map;
    }

    public static void printMapAsLists(Map<String, List<String>> map) {
        for (List<String> list : map.values()) {
            System.out.println(list);
        }
    }
}
[D]
[A, A]
[B, B]
[C]
Return all Duplicates except first occurrence in Object Array with multiple values

Return all Duplicates except first occurrence in Object Array with multiple values


By : user2417667
Date : March 29 2020, 07:55 AM
With these it helps The most straightforward way to do this is by using an array that holds all of the unique items you have found, basically functioning as a set.
The key is that if an item isn’t in that set then it is added to it, and NOT added to duplicates (as it is the first and possibly only occurrence).
code :
let uniqueItems = []
arry.forEach(item => {
  if(uniqueItems.some(other => 
        item.location === other.location
        && .... && ... && ....
        )){
       duplicates.push(item)
  } else {
       uniqueItems.push(item)
  }
}
removing duplicates from an arraylist using this code but ignoring case

removing duplicates from an arraylist using this code but ignoring case


By : pamgo
Date : March 29 2020, 07:55 AM
With these it helps Ok so nothing has really struck me as a good code set to remove duplicates in an ArrayList without creating a whole new array except this code from CarlJohn. I have tried to respond but my rep points are to low.... still.... , use compareToIgnoreCase method of the String class
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