How to increase the size of an array in Java?

Question

I want to store as many elements as desired by the user in an array. But how do I do it.

If I were to create an array, I must do so with a fixed size. Every time a

Answer 1

By using copyOf method in java.util.Arrays class String[] size will increment automatically / dynamically. In below code array size 0 after manipulation of using Arrays.copyOf the size of String array is increased to 4.

package com.google.service;

import java.util.Arrays;

public class StringArrayAutoIncrement {
    public static void main(String[] args) {
        String[] data = new String[] { "a", "b", "c", "d", "e" };
        String[] array = new String[0];// array initialize with zero
        int incrementLength = 1;
        for (int i = 0; i < data.length; i++) {
            array = Arrays.copyOf(data, i + incrementLength);// increment by +1
        }
        /**
         * values of array after increment
         */
        for (String value : array) {
            System.out.println(value);
        }
    }
}

Output:

a
b
c
d
e

Answer 2

On a low level you can do it this way:

long[] source = new long[1];
long[] copy = new long[source.length + 1];
System.arraycopy(source, 0, copy, 0, source.length);
source = copy;

Arrays.copyOf() is doing same thing.

Answer 3

Use an ArrayList. The size it automatically increased if you try to add to a full ArrayList.

Answer 4

u can do it by this

import java.util.Scanner;

class Add
{
  public static void main(String[] args)
  {
     Scanner obj=new Scanner(System.in);
     char ans='y';
     int count=0;
     while(ans!='N'||ans!='n')
     {
       int initial_size=5; 
       int arr[]=new int [initial_size];
       arr[0]=1;
       arr[1]=2;
       arr[2]=3;
       arr[3]=4;
       arr[4]=5;

       if(count>0)
       {
           System.out.print("enter the element u want to add in array: ");
           arr[initial_size-1]=obj.nextInt();
       }
       System.out.print("Do u want to add element in array?");
       ans=obj.next().charAt(0);
       if(ans=='y'||ans=='Y')
       {
         initial_size++;
         count++;
       }             
    }   
  }

}

Answer 5

public class IncreaseArraySize {
 public static void main(String[] args) {
    int arr[] = new int[5];
      for (int i = 0; i < arr.length; i++) {
            arr[i] = 5;
      }
      for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
      }
       System.out.println(" ");
       System.out.println("Before increasing Size of an array :" + arr.length);


        int arr2[] = new int[10];

        arr = arr2;
        arr2 = null;
        for (int i = 0; i < arr.length; i++) {
        System.out.print(arr[i] + " ");
    }
    System.out.println("");
    System.out.println("After increasing Size of an array : " + arr.length);
}
}

Answer 6

You can't. You can either create a new array and move the items to that array - Or you can use an ArrayList.