Question

JAVA JAVA JAVA . I need to convert a string input to int array, for example if user enters 12 / 27 / 2020 , I want to store each value in a separate array and add them afterwards.

Answer 1

For converting string to an int you can use the java method Integer.parseInt()

But this is valid only for a string which is of length more than 0 and is a valid integer.

That is why in you case we cannot directly use this method, instead we have to convert your input in usable format.

For this

• We will first read all of input in a String.
• Traverse this string and whenever we encounter a digit for the first time, we start putting it in a number.
• Once started when we face a non digit character or end of string we stop making this number and then store it in array

Please take a look at the Java code below for better understanding.

import java.util.*;

public class StringToIntArray{
        //method which takes in input string and parses int array from it
        static ArrayList<Integer> convert(String inp){
                ArrayList<Integer> arr = new ArrayList<Integer>();

                //return blank array if input is empty
                if(inp.length()==0)
                        return arr;

                int num=0;
                //this variable keeps a track on wheather we have started making out number
                boolean framing = false; 
                int i=0;
                while(i<inp.length()){
                        //check if it is a digit
                        char x = inp.charAt(i);
                        if(x>='0'&&x<='9'){
                                framing=true;
                                num=num*10+(x-'0'); //extract the numerical digit from char representation
                        }else{
                                if(framing){
                                        //if this character is not a digit and we were making the number,
                                        //then it is time to stop
                                        arr.add(num);

                                        //prepare for next run
                                        num=0;
                                        framing=false;
                                }
                        }
                        i++;
                }
                //Once string ends we might still have a number in process which needs to be added
                if(framing){
                                        //if this character is not a digit and we were making the number,
                                        //then it is time to stop
                                        arr.add(num);

                                        //prepare for next run
                                        num=0;
                                        framing=false;
                }
                return arr;
        }
    public static void main(String args[]) {
      Scanner sc = new Scanner(System.in);
      System.out.println("Enter string with integers.");
      //read all of input in one string
      String inp = sc.nextLine();

      //call conversion method
      ArrayList<Integer> arr = convert(inp);
      System.out.println("Elements in INT array");
      //print output array
      for(int i=0;i<arr.size();i++){
        System.out.print(arr.get(i)+" ");
      }
    }
}

Sample Output