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Java Collection Q&A » ArrayList » Duplicate 

1. How do I remove repeated elements from ArrayList?    stackoverflow.com

I have an ArrayList of Strings, and I want to remove repeated strings from it. How can I do this?

2. Java: Detect duplicates in ArrayList?    stackoverflow.com

How could I go about detecting (returning true/false) whether an ArrayList contains more than one of the same element in Java? Many thanks, Terry Edit Forgot to mention that I am not looking to compare ...

3. Duplicates in Arraylist, comparing various fields java    stackoverflow.com

I have a code to return an arrayList with the duplicates of an ArrayList but seems it's not working, I am comparing all items in the array...

public ArrayList<ObjectList> duplicates(ArrayList<ObjectList> someObjectsList) {

  ...

4. Remove duplicates from a sorted ArrayList while keeping some elements from the duplicates    stackoverflow.com

Okay at first I thought this would be pretty straightforward. But I can't think of an efficient way to solve this. I figured a brute force way to solve this but ...

5. How to remove duplicate entries in an ArrayList    stackoverflow.com


I have an ArrayList<Integer> that is full of years that it pulls from my database i want to know how it is possible to loop through them so i can remove ...

6. Removing Duplicate from Arraylist and Getting the duplicate of one property in a list    stackoverflow.com

i have one arraylist say "templist" it will have items of item say "Stool" now list contains duplicates

1 abc wwww.com lob1
1 abc wwww.com lob2
now i ...

7. Creating an ArrayList of objects with a loop, checking for overlapping objects    stackoverflow.com

I'm making a game for a class and one element of the game is displaying a number of cabbages, which are stored in an ArrayList. This ArrayList must be a fixed ...

8. how to remove arraylist duplicate values    stackoverflow.com

I am performing some maintenance tasks on an old system. I have an arraylist that contains following values:

a,b,12
c,d,3
b,a,12
d,e,3
a,b,12
I used following code to remove duplicate values from arraylist
ArrayList<String> arList;
  public static void ...

9. Would like to avoid duplicate entries in a ArrayList    stackoverflow.com

I am looking for an object like ArrayList that would let me avoid duplicate entries. For example it might have a method that calls 'contains()' to valid each entry before it is ...

10. Find Duplicate Objects in an java arraylist    stackoverflow.com

First of all, I would like to say that I have searched for an answer to this, but did not get an suitable solution. So I have decided to post it ...

11. How can I scan and manipulate an array of strings into a different multi-dimensional array without duplicates?    stackoverflow.com

Sorry of the title is a little bit confusing. What I need to do is read a text file with a bunch of cities and states on separate lines like this:

Salem, ...

12. Java ArrayList Remove duplicates    stackoverflow.com

Hi i have arraylist of custom object , i want to remove duplicate entries ,in my case duplication as follows the object have three field title ,subtitle ,id if ...

13. Finding index of duplicate values in an ArrayList    stackoverflow.com

I have an ArrayList which contains duplicate values at diff diff index. for example {"Indian","American","Chinese","Australian","Indian","Russian","Indian"} as u can see the value - "Indian" exists at index - 0, 4 & 6. I need to ...

14. How to find duplicates in an ArrayList which is in the form of JSON object?    stackoverflow.com

I am having an option in my website for the user i.e: "Settings" in that I given 3 options(TextBoxes) to enter details: 1.E-mail, 2.SMS, 3.MMS.. in this user can enter another ...

15. Finding duplicate elements in an arraylist    stackoverflow.com

I was wondering if there was a way to find duplicate elements in an arraylist. For more context of what I'm trying to do, I have an arraylist of strings. The ...

16. removing duplicates from an arraylist    stackoverflow.com

I am trying to remove duplicate objects from an arraylist see code below:

ArrayList<Customer> customers=new ArrayList<Customer>();

    for(int i=0;i<accounts.size();i++){
        customers.add(accounts.get(i).getCustomer());
    ...

18. Finding duplicate values in arraylist    stackoverflow.com

I have an ArrayList<Car> For Example

class Car{
   String carName;
   int carType;
}
Now, I have to find if the list has any cars having same name. What is the ...

19. how combine between two arraylist if has same value    stackoverflow.com

sorry if i confusing, i have two arraylist as below

al1 - [Consignment, Bank, Custodian, Rejected, Bank]
al2 - [[2, 0, 0, 0, 0, 0, 0],
       [6, ...

20. Removing an object from the duplicate ArrayList only    stackoverflow.com

I've copied an ArrayList over as so:

MyList2 = MyList1;
In an attempt to load MyList2's objects with the ones which MyList1 has. Now as I iterate through MyList2, I it.remove() some objects, but ...

21. Adding duplicates in an ArrayList    stackoverflow.com

I am stuck On how to find duplicates in an ArrayList and then manipulate them. I am implementing a polynomial class and I want to add monomials of the same ...

22. How to remove duplicate from ArrayList?    coderanch.com

The way you show us here most likely does not work because you have not added hashCode() and equals() methods to your class MyClass. You must add these methods so that HashSet can properly detect when two MyClass objects are equal. See the description of the methods hashCode() and equals() in the API documentation of class java.lang.Object for details on how ...

23. Eliminating Duplicate in Arraylist and moving the dups to another arraylist.    coderanch.com

Hi Ranchers, Can you please help me with this problem. I have a master arraylist say A1 which hase values like Red, Blue, Green I have to copy unique/non duplicate values from another arraylist say A2 to A1. Whenever there is a duplicate value in A2 which corresponds to A1 the value should be stored in another arraylist A3. This is ...

25. How do I remove duplicates from an arraylist of objects from another class ? -EDITED    coderanch.com

Hi, I have a class called Switch which has as a constructor parameter an integer. In another class called Network, in a method I create 2 instances of Switch, a and b. I am adding the 2 objects to an arraylist of type Switch called switchList. How can I compare the integer values of the objects so I can find duplicates ...

27. How to avoid duplicate element in ArrayList?    coderanch.com

Hi All, How to avoid duplicate element/Values in ArrayList?This was interview question. My Answer was better to use Set in place of ArrayList.When collection framework has such facility better to use that to avoid duplicate elements. But interviewer was said no i want it only in ArrayList.I suggest to use equals and override it with hashcode and make some sort of ...

28. Remove duplicates in arraylist    coderanch.com

import java.util.*; public class ArrayListRemoveDuplicates { public static void main(String args[]) { ArrayList al1=new ArrayList(); al1.add("raja"); al1.add("raja"); al1.add("tendulkar"); al1.add("prakash"); al1.add("sachin"); al1.add("sachin"); al1.add("zaheer"); al1.add("asin"); al1.add("surya"); Set set = new HashSet(); set.addAll(al1); System.out.println("Arraylist " + al1); System.out.println("Set " + set); } } Output : Arraylist [asin, prakash, raja, raja, sachin, sachin, surya, tendulkar, zaheer] Set [surya, zaheer, sachin, asin, tendulkar, raja, prakash]

29. How to find duplicate values in ArrayList with out iterarting..?    coderanch.com

Hi All I need to find duplicate values in ArrayList is there any method to find duplicate values..? Example List list = new ArrayList(); list.add("a"); list.add("a"); list.add("b"); list.add("c"); list.add("c"); Here a and c are duplicate values. i need the output as [a,c] I already done using set but i need Any API to solve *i need not use any iteration logic ...

31. How to remove duplicate values from ArrayList    forums.oracle.com

import java.util.Scanner; import java.util.ArrayList; public class MainClass { public static void main(String args[]) { ArrayList list = new ArrayList(); Scanner in = new Scanner(System.in); int input=0; while(true) { input = in.nextInt(); if(input<=0) { System.out.println("Exit"); break; } else list.add(input); } for(int i=0; i

32. Finding a duplicate item in an arraylist.    forums.oracle.com

Hi all, I have an arraylist with the items listed below. ArrayList result = new ArrayList(); UserID Name rightRole 1. { 123, george , Y} 2. { 123 , grorge , N} 3. { 456, chris, Y} Now i want to identify those users with duplicate entires in the list (Eg. George) and keep only one item with Right Role 'Y' ...

33. finding duplicates in arraylist by using contains method    forums.oracle.com

How can I find the duplicates in an arraylist by using the contains method? then I need to store every duplicate in another arraylist so lets say my arraylist is <1,2,2,3,3,2,1,3,4,5> so I need to find the duplicates which are 1,2 and 3 and store those duplicates in another arraylist so this arraylist will be something like this <1,2,3> and I ...

34. Finding and removing duplicates in an Arraylist of beans.    forums.oracle.com

Hi, I have an arraylist of beans from which I need to remove the duplicate entries. To elaborate, My bean has three field, name,age and indicator. At Present the arraylist contains duplicate entries. I want to get a final list in such a way that, the names are distince.If there are two beans with the same name, I want the bean ...

35. remove duplicates from ArrayList    forums.oracle.com

Hi, I am sorry for asking a simple question. I have an ArrayList which contains Location objects. Location is a bean class with LocationId, Name, Address etc.. Now I want to remove duplicates from this ArrayList. We know whether duplicates exist or not by checking LocationId of Location object. LocationId is int. How can I remove duplicates from this ArrayList? I ...

36. HashSet made up of Elements of an ArrayList not eliminating duplicates.    forums.oracle.com

The problem is that equals() and hashCode() aren't implemented for your arrays. When it autoboxes your arrays to Double[], those methods default to Object's implementation of equals() and hashCode(), which does instance comparison instead of value comparison. I recommend wrapping your double arrays into a custom class that overrides equals() and hashCode() based on the values in the array and not ...

37. Extract from ArrayList without duplicate    forums.oracle.com

38. Adding to an ArrayList without getting duplicates    forums.oracle.com

Alright I'm stuck here, I'm trying to add integers to an ArrayList without getting duplicates. I am aware of the boxing and auto unboxing of the int to Integer type. This is the code I have but I get a memory error when i try to run it. numberlist is an Array List declared earlier by ArrayList public void addLineNumber(int lineNumber){ ...

40. Problem with removing duplicates from ArrayList    forums.oracle.com

System.out.println(arList); Object arListArray[] = arList.toArray(); int arrSize = arListArray.length; for(int i = 0; i < arrSize; i++) { for(int j = 0; j < arrSize; j++) { if(i == j) { continue; } else { if (arListArray == arListArray[j]) { for (int k = j; k < arrSize - 1; k++) arListArray[k] = arListArray[k + 1]; arrSize--; } } } } ...

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