How to find subsets of a given string

import java.util.HashSet;
import java.util.Scanner;
import java.util.Set;

//Define the functional interface with single abstract method.
interface SubsetsOfStr {
	Set<String> subsets(String strVar);
}

public class SubsetsOfString {

	public static void main(String[] args) {

		Scanner inpStr = new Scanner(System.in);
		System.out.println("Enter an input word for which you need all the sub sets of strings");
		String inpWord = inpStr.next();

		/*
		 * Define the Lambda expression for the user defined 'SubsetsOfStr' functional
		 * interface
		 */
		SubsetsOfStr ss = ((strVal) -> {
			int sizeOfSubstr = 1, beginIdx = 0, endIdx = 1;
			Set<String> finalSubsetStrs = new HashSet<String>();

			// Iterate the loop until the substring's length is equals with length of the
			// actual string
			while (sizeOfSubstr <= strVal.length()) {

				// Iterate the substring sized loop until the subscript less than or equals the
				// actual length
				while (beginIdx < strVal.length() && endIdx <= strVal.length())
					finalSubsetStrs.add(strVal.substring(beginIdx++, endIdx++));

				/*
				 * Increment size of sub string 'sizeOfSubstr' by 1, reset 'beginIdx' and assign
				 * next sized substring to 'endIdx' for the next iteration
				 */
				sizeOfSubstr++;
				beginIdx = 0;
				endIdx = sizeOfSubstr;
			}
			return finalSubsetStrs;
		});

		System.out.println("All the unique substrings from the given String=" + inpWord + " are below");
		System.out.println(ss.subsets(inpWord));
		System.out.println("All the unique substrings of another string `MIKE` are" + ss.subsets("MIKE"));
		System.out.println("All the unique substrings of another string `VALLI` are" + ss.subsets("VALLI"));
		inpStr.close();
	}
}