How to remove duplicates from arraylist in java

How do you remove duplicates from ArrayList in Java?


  1. Get the ArrayList with duplicate values.
  2. Create a new List from this ArrayList.
  3. Using Stream(). distinct() method which return distinct object stream.
  4. convert this object stream into List.

How do you remove duplicates from an ArrayList in Java 8?

Remove duplicates in arraylist – Java 8. To remove the duplicates from the arraylist, we can use the java 8 stream api as well. Use steam’s distinct() method which returns a stream consisting of the distinct elements comparing by object’s equals() method. Collect all district elements as List using Collectors.

How do I remove duplicates from a list?

There is no official method that should be used to remove duplicates from a list, but the most common approaches are to use the dictionary fromkeys() function or convert your data into a set.

How do you remove duplicates from a set in Java?


  1. Take a Set.
  2. Insert all array element in the Set. Set does not allow duplicates and sets like LinkedHashSet maintains the order of insertion so it will remove duplicates and elements will be printed in the same order in which it is inserted.
  3. Convert the formed set into array.
  4. Print elements of Set.

Can ArrayList have duplicates?

4) Duplicates: ArrayList allows duplicate elements but HashMap doesn’t allow duplicate keys (It does allow duplicate values). 5) Nulls: ArrayList can have any number of null elements. … In HashMap the elements is being fetched by specifying the corresponding key.

How do you remove duplicates in ArrayList without using set?

Remove duplicates from arraylist without using collections

  1. package arrayListRemoveduplicateElements;
  2. import java.util.ArrayList;
  3. public class RemoveDuplicates {
  4. public static void main(String[] args){
  5. ArrayList<Object> al = new ArrayList<Object>();
  6. al.add(“java”);
  7. al.add(‘a’);
  8. al.add(‘b’);
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Does list allow duplicates in Java?

List in Java allows duplicates while Set doesn’t allow any duplicate. If you insert duplicate in Set it will replace the older value. Any implementation of Set in Java will only contains unique elements. … List is an Ordered Collection while Set is an unordered Collection.

Does Set allow duplicates in Java?

The meaning of “sets do not allow duplicate values” is that when you add a duplicate to a set, the duplicate is ignored, and the set remains unchanged. This does not lead to compile or runtime errors: duplicates are silently ignored.24 мая 2014 г.

How do you find duplicates in ArrayList?

Find duplicate user-defined objects in a list

  1. package com.javadeveloperzone; import java.util.Objects; public class Employee { int empId; String empName; String empAddress; …
  2. List<Employee> employees = new ArrayList. employees. add(new Employee(1, employees. add(new Employee(2, …
  3. 2==>Frank. 1==>John. 2==>Frank 1==>John.

How do you remove duplicates from an array?

1) Remove Duplicate Element in Array using Temporary Array

  1. public class RemoveDuplicateInArrayExample{
  2. public static int removeDuplicateElements(int arr[], int n){
  3. if (n==0 || n==1){
  4. return n;
  5. }
  6. int[] temp = new int[n];
  7. int j = 0;
  8. for (int i=0; i<n-1; i++){

How do I remove duplicates from a list in Excel?

Follow these steps:

  1. Select the range of cells, or ensure that the active cell is in a table.
  2. On the Data tab, click Remove Duplicates (in the Data Tools group).
  3. Do one or more of the following: …
  4. Click OK, and a message will appear to indicate how many duplicate values were removed, or how many unique values remain.
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How do you remove duplicates in Python?

Pandas drop_duplicates() method helps in removing duplicates from the data frame.

  1. Syntax: DataFrame.drop_duplicates(subset=None, keep=’first’, inplace=False)
  2. Parameters: …
  3. inplace: Boolean values, removes rows with duplicates if True.
  4. Return type: DataFrame with removed duplicate rows depending on Arguments passed.

Does HashSet remove duplicates?

HashSet cannot contain duplicate values.

Removing elements from a HashSet

  • Remove an element from a HashSet.
  • Remove all the elements that exist in a given collection from the HashSet.
  • Remove all the elements that satisfy a given predicate from the HashSet.
  • Clear the HashSet completely by removing all the elements.

Does linked list allow duplicates?

1) Both ArrayList and LinkedList are an implementation of List interface, which means you can pass either ArrayList or LinkedList if a method accepts the java. util. … 4) ArrayList and LinkedList also allow duplicates and null, unlike any other List implementation e.g. Vector.

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