java compare arraylists for equality

Java ArrayList - how can I tell if two lists are equal, order not mattering?

stackoverflow.com › questions › 13501142 › java-arraylist-how-can-i-tell-if-two-lists-are-equal-order-not-mattering

Probably the easiest way for any list would be:

listA.containsAll(listB) && listB.containsAll(listA)

Answer from user381105 on Stack Overflow

How to do in Java

howtodoinjava.com › home › collections framework › java arraylist › compare two lists in java: equality, differences, common items

Compare Two Lists in Java: Equality, Differences, Common Items

1 week ago - List<String> warehouse = List.of("apple", "banana", "cherry"); List<String> shop = List.of("cherry", "banana", "date"); List<String> reordered = List.of("banana", "cherry", "apple"); boolean equal = warehouse.equals(shop); // false boolean sameIgnoringOrder = warehouse.stream().sorted().toList() .equals(reordered.stream().sorted().toList()); // true List<String> onlyInWarehouse = new ArrayList<>(warehouse); onlyInWarehouse.removeAll(shop); // [apple] List<String> missingInWarehouse = new ArrayList<>(shop); missingInWarehouse.removeAll(warehouse); // [date] List<String> common = new ArrayList<>

GeeksforGeeks

geeksforgeeks.org › java › comparing-two-arraylist-in-java

Comparing two ArrayList In Java - GeeksforGeeks

January 23, 2026 - Two ArrayList objects list1 and list2 are created. list1.equals(list2) checks if both lists are equal (same size and elements in the same order).

TutorialsPoint

tutorialspoint.com › comparing-two-arraylist-in-java

Check two ArrayList for equality in Java

June 18, 2024 - Two ArrayList can be compared to check if they are equal or not using the method java.util.ArrayList.equals(). This method has a single parameter i.e. an ArrayList that is compared with the current object.

DevQA

devqa.io › java-compare-two-arraylists

Java Compare Two Lists

March 17, 2020 - import java.util.Arrays; import java.util.Collections; import java.util.List; public class CompareTwoLists { public static void main(String[] args) { List<String> listOne = Arrays.asList("b", "c", "a"); List<String> listTwo = Arrays.asList("a", "c", "b"); List<String> listThree = Arrays.asList("c", "a", "b"); Collections.sort(listOne); Collections.sort(listTwo); Collections.sort(listThree); boolean isEqual = listOne.equals(listTwo); System.out.println(isEqual); isEqual = listOne.equals(listThree); System.out.println(isEqual); } } Output: true true · The List interface also provides methods to

Javaprogramto

javaprogramto.com › 2020 › 04 › how-to-compare-two-arraylist-for-equality-in-java.html

How to compare two ArrayList for equality in Java 8? ArrayList equals() or containsAll() methods works?

June 13, 2021 - // list 2 List<String> listB = ... listB.add("linkedlist"); // comparing two lists boolean isEqualAllValues = listA.containsAll(listB); System.out.println(isEqualAllValues); Output: ... Now, it is time to write the same logic ...

Stack Overflow

stackoverflow.com › questions › 13501142 › java-arraylist-how-can-i-tell-if-two-lists-are-equal-order-not-mattering

Java ArrayList - how can I tell if two lists are equal, order not mattering? - Stack Overflow

Top answer

1 of 16

190

Probably the easiest way for any list would be:

listA.containsAll(listB) && listB.containsAll(listA)

2 of 16

144

You could sort both lists using Collections.sort() and then use the equals method. A slighly better solution is to first check if they are the same length before ordering, if they are not, then they are not equal, then sort, then use equals. For example if you had two lists of Strings it would be something like:

public  boolean equalLists(List<String> one, List<String> two){     
    if (one == null && two == null){
        return true;
    }

    if((one == null && two != null) 
      || one != null && two == null
      || one.size() != two.size()){
        return false;
    }

    //to avoid messing the order of the lists we will use a copy
    //as noted in comments by A. R. S.
    one = new ArrayList<String>(one); 
    two = new ArrayList<String>(two);   

    Collections.sort(one);
    Collections.sort(two);      
    return one.equals(two);
}

TutorialsPoint

tutorialspoint.com › how-to-compare-two-arraylist-for-equality-in-java

How to compare two ArrayList for equality in Java?

July 30, 2019 - Java Object Oriented Programming Programming · You can compare two array lists using the equals() method of the ArrayList class, this method accepts a list object as a parameter, compares it with the current object, in case of the match it ...

w3resource

w3resource.com › java-exercises › collection › java-collection-exercise-13.php

Java - Compare two array lists

import java.util.*; public class Exercise13 { public static void main(String[] args) { ArrayList<String> c1= new ArrayList<String>(); c1.add("Red"); c1.add("Green"); c1.add("Black"); c1.add("White"); c1.add("Pink"); ArrayList<String> c2= new ArrayList<String>(); c2.add("Red"); c2.add("Green"); c2.add("Black"); c2.add("Pink"); //Storing the comparison output in ArrayList<String> ArrayList<String> c3 = new ArrayList<String>(); for (String e : c1) c3.add(c2.contains(e) ?

javaspring

javaspring.net › blog › java-compare-unordered-arraylists

How to Compare Unordered ArrayLists in Java: Efficiently Check for Same Elements Regardless of Order — javaspring.net

By default, the `equals()` method of `ArrayList` checks for **strict equality**: two lists are considered equal only if they have the same elements in the **same order**, with the same frequencies.

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Apps Developer Blog

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Compare two ArrayList in Java - Apps Developer Blog

August 16, 2022 - class Test { public static void main(String[] args) { List<Integer> list1 = new ArrayList<>(Arrays.asList(1, 2, 3, 4)); // list2 is equal to list 2 List<Integer> list2 = new ArrayList<>(Arrays.asList(1, 2, 3, 4)); // list3 has the same elements but in diff order List<Integer> list3 = new ArrayList<>(Arrays.asList(3, 1, 4, 2)); // list4 is not the same List<Integer> list4 = new ArrayList<>(Arrays.asList(3, 7, 9, 2)); System.out.println("list1 == list2: " + CollectionUtils.isEqualCollection(list1, list2)); System.out.println("list1 == list3: " + CollectionUtils.isEqualCollection(list1, list3)); System.out.println("list1 == list4: " + CollectionUtils.isEqualCollection(list1, list4)); } }

Javatpoint

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How to Compare Two ArrayList in Java - Javatpoint

Java program to determine whether two trees are identical

reddit.com › r/learnprogramming › a question about the comparison of elements in two arraylists in java.

r/learnprogramming on Reddit: A question about the comparison of elements in two ArrayLists in java.

April 21, 2023 -

I'm trying to do my homework

I created two ArraLists of Integer, and the content in the list is as follows:

List1:

5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 105 110 115 120 125 130 135 140 145 150

List2:

150 300 450 600 750

when i use

list1. get(list1. size() - 1) == list2. get(0);

I get false;

I have to use

list1.get(list1.size() - 1).equals(list2.get(0));

to get true;

Then I try the following code:

ArrayList<Integer> arrList1 = new ArrayList<Integer>();

ArrayList<Integer> arrList2 = new ArrayList<Integer>();

arrList1. add(10);

arrList2.add(10);

System.out.println(arrList1.get(0) == arrList2.get(0));

I get true;

I know that == can only be used to compare values, or Primitive types, while .equals() is used to compare references.

I'm sure what I'm storing in the ArrayList is integer, int, so why can't I use == for comparison? (And I'm also wondering why comparing 10 with == gets true and 150 gets false)

I wonder why this is happening?

Thanks in advance to everyone who helped me.

Top answer

1 of 1

I know that == can only be used to compare values, or Primitive types, while .equals() is used to compare references. Yes, you can use == to compare two int values, but you must use equals() to compare two Integer objects. ArrayLists contain Integers, and not int. This is why their type is ArrayList -- they are a list of Integer objects. If you have two Integer objects, you should use equals to compare the two. If you use ==, it will sometimes evaluate to true, and sometimes evaluate to false. It is best not to rely on the nuances of this behavior. If you really want to know, Integers with values between -128 and 127 are typically cached -- see https://docs.oracle.com/javase/7/docs/api/java/lang/Integer.html#valueOf(int) See https://www.online-java.com/DIQTngFfxJ as an example

Medium

aryan-kapoor4564.medium.com › how-to-compare-two-arraylist-in-java-83336458880

How to compare two ArrayList in Java? | by Aryan Kapoor | Medium

March 16, 2020 - With the help of the equals() method, we can compare two ArrayList in java and check whether they are the same or not. But, here is a condition, the order of the elements of both the ArrayList must be the same.

Medium

medium.com › @QA-initi › how-to-compare-two-array-list-in-java-using-comparator-cc05617175b5

How to compare two array list in Java using Comparator | by QA-init | Medium

November 14, 2023 - ArrayList<Integer> list1 = new ... comparator); Collections.sort(list2, comparator); After this, we can use the equals() method to compare the two ArrayList....

javaspring

javaspring.net › blog › how-to-compare-arraylists-in-java

Comparing ArrayLists in Java: A Comprehensive Guide — javaspring.net

Custom Comparison: Comparing elements based on specific business rules, such as comparing objects by a particular property. The equals method in ArrayList checks if two lists are equal.

Java Guides

javaguides.net › 2024 › 06 › java-arraylist-equals-method.html

Java ArrayList equals() Method

June 11, 2024 - ▶️ For AI, ChatGPT, Web, Tech, and Generative AI, subscribe to another channel: Ramesh Fadatare on YouTube ... The ArrayList.equals() method in Java is used to compare two ArrayList instances for equality.

DEV Community

dev.to › aryan19694946 › how-to-compare-two-arraylist-in-java-499b

How to compare two ArrayList in Java? - DEV Community

March 19, 2020 - With the help of the equals() method, we can compare two ArrayList in java and check whether they are the same or not. But, here is a condition, the order of the elements of both the ArrayList must be the same.

GeeksforGeeks

geeksforgeeks.org › java › list-equals-method-in-java-with-examples

List equals() Method in Java with Examples - GeeksforGeeks

January 3, 2025 - // Java code to show the implementation ... l2 = new ArrayList<>(); l2.add(1); l2.add(2); if (l.equals(l2)) System.out.println("Equal"); else System.out.println("Not equal"); } } ... Parameters: This function has a single parameter ...

javathinking

javathinking.com › blog › how-to-compare-equality-of-lists-of-arrays-with-modern-java

How to Compare Equality of Lists of Arrays in Modern Java 8 (and Java 9 Enhancements) — javathinking.com

For each index, compare the arrays element-wise (not by reference). Java 8 introduced the Stream API, which provides a clean and efficient way to iterate over collections and perform element-wise checks. Below are three Java 8 approaches to compare lists of arrays. Before comparing elements, always check if the lists have the same size. If not, they can’t be equal.

YouTube

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#7 - How to Compare Two ArrayLists in Java - YouTube

10:31

In this video, I have explained how to compare two ArrayLists in Java.Learn:1. Compare two ArrayList using Sort and Equals methods.2. Find out the additional...

Published: October 19, 2020

Views: 52K