Java Program to Convert String to Integer Array

24 Sep, 2021
Strings – Strings in Java are objects that are supported internally by a char array. Since arrays are immutable, and strings are also a type of exceptional array that holds characters, therefore, strings are immutable as well. 
Integer Array – An array is a combination of the same type of variables. Likewise, a collection of integers (int) referred to by a common name is an Integer Array.
Problem Statement – Given a string, the task is to convert that string into an integer array. 
Let us first go through few examples to make it more clear.
Examples:
Input  : String : "1 23 456 7890"
Output : Integer array : [1 23 456 7890]
Input  : String : "[1,2,356,678,3378]"
Output : Integer array : [1, 2, 356, 678, 3378]
There are numerous approaches to do the same; a few of them are listed below.
Methods:
Using string.replaceAll() methodUsing string.split() method
Using string.replaceAll() method
Using string.split() method
The string.replaceAll() method takes two arguments, a regex, and the replacement values. This method will replace the given regex with the given replacement value, and after that, the split() method is used to split the string.
Java
// Java Program to Convert String to Integer Array// Using string.replaceAll() method // Importing input output and utility classesimport java.io.*;import java.util.Arrays; public class GFG {    public static void main(String[] args)    {        // declaring the string        String str = "[1,2,356,678,3378]";         // calling replaceAll() method and split() method on        // string        String[] string = str.replaceAll("\\[", "")                              .replaceAll("]", "")                              .split(",");         // declaring an array with the size of string        int[] arr = new int[string.length];         // parsing the String argument as a signed decimal        // integer object and storing that integer into the        // array        for (int i = 0; i < string.length; i++) {            arr[i] = Integer.valueOf(string[i]);        }         // printing string        System.out.print("String : " + str);         // printing the Integer array        System.out.print("\nInteger array : "                         + Arrays.toString(arr));    }}
String : [1,2,356,678,3378]
Integer array : [1, 2, 356, 678, 3378]
The string.split() method is used to split the string into various sub-strings. Then, those sub-strings are converted to an integer using the Integer.parseInt() method and store that value integer value to the Integer array.
Java
// Java Program to Convert String to Integer Array// Using string.split() method // Importing input output and utility classesimport java.io.*; public class GFG {    // Function for conversion    static int[] method(String str)    {         String[] splitArray = str.split(" ");        int[] array = new int[splitArray.length];         // parsing the String argument as a signed decimal        // integer object and storing that integer into the        // array        for (int i = 0; i < splitArray.length; i++) {            array[i] = Integer.parseInt(splitArray[i]);        }        return array;    }     // main method    public static void main(String[] args)    {        // Bufferedreader declaration        BufferedReader br = new BufferedReader(            new InputStreamReader(System.in));         // string declaration        String str = "1 23 456 7890";        int i;         // declaring the variable & calling the method with        // passing string as an argument        int[] array = method(str);         // printing the string        System.out.print("\nString : " + str);         // printing the Integer array        System.out.print("\nInteger array : [");        for (i = 0; i < array.length; i++) {            System.out.print(array[i] + " ");        }         System.out.print("]");    }}
String : 1 23 456 7890
Integer array : [1 23 456 7890 ]
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