Recursively Search for String in Java

Illustrating searching string recursively in Java and getting it's indexes & also no.of times the string occurred.  This logic is easy and simple. Here is an example program.

import java.util.*;

class RecursiveStringSearch

{

	public static void main(String args[])

	{

	Scanner s=new Scanner(System.in);

	System.out.println("Enter main string");

	String st=s.nextLine();

	System.out.println("Enter search string");

	String se=s.nextLine();

	int idx=-1;

	int i;

		for(i=0;i<st.length();i++)

		{

		idx=st.indexOf(se,i+idx);

			if(idx==-1)break;

		System.out.println("Found at index "+idx);

		}

	System.out.println("Totally found "+i+" times.");

	}

}

Recursive String Search Output

Enter main string

this is a sample test.

Enter search string

is

Found at index 2

Found at index 5

Totally found 2 times.

Explaining The Logic

Make the idx=-1 which indicates that the string is not found at first.

int i is for counting the no.of times the string occurred.

Loop till the end of the main string, the string in which the search has to go.

idx=st.indexOf(se,i+idx); which updates the value of idx with the index of the search string in the main string. i+idx is because when the loop updates, the next search has to start after the last index.

if(idx==-1)break; Exit the loop if the string is not found. Whenever the string is not found, the loop is terminated.

i is the value which is nothing but the no.of times the string had occurred in the main string. Because i value will be updated only with the no.of times the string is according to the logic.