add element to array java

stackoverflow.com › questions › 2843366 › how-to-add-new-elements-to-an-array

The size of an array can't be modified. If you want a bigger array you have to instantiate a new one.

A better solution would be to use an ArrayList which can grow as you need it. The method ArrayList.toArray( T[] a ) gives you back your array if you need it in this form.

List<String> where = new ArrayList<String>();
where.add( ContactsContract.Contacts.HAS_PHONE_NUMBER+"=1" );
where.add( ContactsContract.Contacts.IN_VISIBLE_GROUP+"=1" );

If you need to convert it to a simple array...

String[] simpleArray = new String[ where.size() ];
where.toArray( simpleArray );

But most things you do with an array you can do with this ArrayList, too:

// iterate over the array
for( String oneItem : where ) {
    ...
}

// get specific items
where.get( 1 );

Answer from tangens on Stack Overflow

Stack Overflow

stackoverflow.com › questions › 2843366 › how-to-add-new-elements-to-an-array

java - How to add new elements to an array? - Stack Overflow

Top answer

1 of 16

478

The size of an array can't be modified. If you want a bigger array you have to instantiate a new one.

A better solution would be to use an ArrayList which can grow as you need it. The method ArrayList.toArray( T[] a ) gives you back your array if you need it in this form.

List<String> where = new ArrayList<String>();
where.add( ContactsContract.Contacts.HAS_PHONE_NUMBER+"=1" );
where.add( ContactsContract.Contacts.IN_VISIBLE_GROUP+"=1" );

If you need to convert it to a simple array...

String[] simpleArray = new String[ where.size() ];
where.toArray( simpleArray );

But most things you do with an array you can do with this ArrayList, too:

// iterate over the array
for( String oneItem : where ) {
    ...
}

// get specific items
where.get( 1 );

2 of 16

124

Use a List<String>, such as an ArrayList<String>. It's dynamically growable, unlike arrays (see: Effective Java 2nd Edition, Item 25: Prefer lists to arrays).

import java.util.*;
//....

List<String> list = new ArrayList<String>();
list.add("1");
list.add("2");
list.add("3");
System.out.println(list); // prints "[1, 2, 3]"

If you insist on using arrays, you can use java.util.Arrays.copyOf to allocate a bigger array to accomodate the additional element. This is really not the best solution, though.

static <T> T[] append(T[] arr, T element) {
    final int N = arr.length;
    arr = Arrays.copyOf(arr, N + 1);
    arr[N] = element;
    return arr;
}

String[] arr = { "1", "2", "3" };
System.out.println(Arrays.toString(arr)); // prints "[1, 2, 3]"
arr = append(arr, "4");
System.out.println(Arrays.toString(arr)); // prints "[1, 2, 3, 4]"

This is O(N) per append. ArrayList, on the other hand, has O(1) amortized cost per operation.

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Discussions

How to add something to primitive array in Java?

Allocate a new bigger array, copy existing values over, add the new one. You probably don't really want to be using an array for what you're doing if you're doing this a lot. More on reddit.com

r/learnprogramming

December 2, 2015

Adding Items to an array in Java - Stack Overflow

I wanted to create an array that has a length specified by the user, and also wanted to have it filled by a loop command, and then it should be copied to another array by another loop command, so I... More on stackoverflow.com

stackoverflow.com

List vs Array vs ArrayList

These are three different things: Array - a very basic data structure. It has a fixed, predetermined size that must be known at the time of creating (instantiating) the array. Think of it as a sorting box with several slots. Here, you have .length - without parentheses as it is a property, not a method List - an interface (not a class) that defines certain behavior. It cannot be instantiated on its own. ArrayList - a concrete class that implements the List interface. When you see a declaration like List data = new ArrayList<>(); there are several things going on: Listprogramming against the interface - here, the interface List is used as data type - this is good practice as it allows you to at any time change the internal representation of the List - e.g. from ArrayList to LinkedList if you figure out that the other better suits your needs. this is a data type identifier. It limits the type of elements that can be stored in the list. Here, only String objects are allowed. If you were to omit this, the list would store Object (the ancestor of all Java classes) and descendant instances (i.e. Object and any subclass of it). data - just the variable name new - the keyword to create a new Object Instance ArrayList<>() - the constructor call. Here, the constructor without parameters of the ArrayList class is called. The diamond operator <> is used to infer (take) the data type for the ArrayList from the variable type (here String). So, the whole is: we create a new variable of type List that can only accept String elements and ist internally represented as ArrayList. More on reddit.com

r/javahelp

September 12, 2023

Adding objects to array list - Last entry overwrites all elements

You are only creating one instance of the class Recipe. And you are adding it multiple times to the ArrayList. This will modify the object everytime.

What you need to do instead is to create a new Recipe before setting the name, and then add it to the ArrayList.

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GeeksforGeeks

geeksforgeeks.org › java › arrays-in-java

Arrays in Java - GeeksforGeeks

08:32

This Java program demonstrates how to pass an array to a method. An integer array arr is declared and initialized in the main method. The sum() method is called with arr as an argument. Inside the sum() method, all array elements are added using a for loop.

Published May 8, 2026

reddit.com › r/learnprogramming › how to add something to primitive array in java?

r/learnprogramming on Reddit: How to add something to primitive array in Java?

December 2, 2015 -

Hi all, so I have an empty array I just created like this:

int[] array = new int[5];

How do I add numbers to it? I tried array.append() but it's not working. I don't want to do it manually like array[0] etc I want to just keep adding to the tail.

EDIT: I'm sure I won't go over the limit of what the array can contain. I just want to know how to add to the tail of the array without having to specify what position is being added.

Top answer

1 of 2

You have two problems in your code.

Substitute your for(s) with the following code:

    for (int i = 0; i < n; i++) {
        int element = input.nextInt(); //elemet inserted by the user
        array1[i] = element;
    }

    for (int i = 0; i < n; i++) {
        array2[i] = array1[i];
    }

2 of 2

for add item in array

 for (int i = 0; i < n; i++) {
        int index = input.nextInt();
        array1 [i] = index ;
    }

W3Schools

w3schools.com › java › ref_arraylist_add.asp

Java ArrayList add() Method

import java.util.ArrayList; public ... cars.add("Ford"); cars.add("Mazda"); System.out.println(cars); } } ... The add() method adds an item to the list....

Oracle

docs.oracle.com › javase › 8 › docs › api › java › util › ArrayList.html

ArrayList (Java Platform SE 8 )

April 21, 2026 - NullPointerException - if the specified array is null ... Returns the element at the specified position in this list. ... Replaces the element at the specified position in this list with the specified element. ... Appends the specified element to the end of this list. ... Inserts the specified element at the specified position in this list. Shifts the element currently at that position (if any) and any subsequent elements to the right (adds one to their indices).

JanBask Training

janbasktraining.com › community › java › how-to-add-new-elements-to-an-array

How to add new elements to an array? - Java

September 2, 2025 - Use unshift() to add elements at the beginning. Use splice() to insert elements at any position. ... Arrays in Java have fixed sizes, so you can’t directly add elements.

Tutorjoes

tutorjoes.in › java_programming_tutorial › Insert_element_array_in_java

Insert an element (specific position) into an array in Java

After shifting the elements, the program sets the element at the specified index to the new value. Finally, the program prints the updated array using · Arrays.toString(a) and stores the result in a string. import java.util.Arrays; public class Insert_element_array { public static void main(String args[]) { //Program to insert a element in specific index of an array int[] a = {10,20,30,40,50,60,70,80,90,100}; int index = 2; int value = 55; System.out.println("Before Insert "+Arrays.toString(a) ); for(int i=a.length-1;i>index;i--) { a[i]=a[i-1]; } a[index]=value; System.out.println("After Insert "+Arrays.toString(a) ); } }

Edureka Community

edureka.co › home › community › categories › java › how can i add new elements to an array in java

How can I add new elements to an Array in Java | Edureka Community

April 19, 2018 - I want to append elements to an array String[] mm= {"5","4","3"}; mm.append("2"); This ... give me a way in which I can add elements to this array.

iO Flood

ioflood.com › blog › java-add-to-array

Adding Elements to an Array in Java: A How-To Guide

February 27, 2024 - But think of Java arrays as a train that can add more carriages, accommodating more passengers, or in this case, elements. This guide will walk you through the process of adding elements to an array in Java, from the basics to more advanced techniques.

DigitalOcean

digitalocean.com › community › tutorials › java-list-add-addall-methods

How To Use add() and addAll() Methods for Java List | DigitalOcean

September 10, 2025 - Use add(int index, E element) for single elements or addAll(int index, Collection<? extends E> c) for multiple elements: list.add(2, "middle"); list.addAll(1, Arrays.asList("A", "B")); Mastering Java’s add() and addAll() methods is essential for efficient programming.

Study.com

study.com › business courses › java programming tutorial & training

Adding to Arrays in Java - Lesson | Study.com

January 13, 2019 - Some programming languages support dynamic arrays, which are arrays that let you add to the end. Java does not. The following code tries to add a sixteenth element to the array. Don't forget that Java starts counting at zero! We've set the size to 15, so when we're adding at the index of 15, ...

CodeGym

codegym.cc › java blog › java arrays › how to add a new element to an array in java

How To Add an Element To an Array in Java

September 28, 2023 - Add all the elements of the previous data range to the new one, as well as the new values. Print the resulting array. Try creating such an array on your own and compare your code to that in the example below: // Java Program to add an element in an Array import java.lang.*; import java.util.*; class ArrayDemo { //Method to add an element x into array myArray public static int[] addX(int myArray[], int x) { int i; // create a new array of a bigger size (+ one element) int newArray[] = new int[myArray.length + 1]; // insert the elements from the old array into the new one for (i = 0; i < myArray

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