Question

1.This is a problem from our midterm. HOWEVER, you must use functions to solve the problem this time.(using Java please!)

Write a program that prompts the user to enter two strings s1 and s2 and reports whether s2 is a substring of s1. The matching should be case-sensitive. The ONLY String class methods you are allowed to use is charAt(index) and length().

Answer 1

CODE in Java:

import java.util.Scanner; // For input from user.

public class CheckSubString{

// Method for checking if s2 is a substring of s1 or not.
// It returns true if s2 is a substring of s1 otherwise false.
public static boolean checkSubString(String s1, String s2)
{
// for keeping track of s2 if it is matching completely or not
// character by character.
boolean checkSS = false;
  
// loop from starting character of s1 to the character where length
// of s2 can be fitted. Like if
// s1 is "checkcheck" and s2 is "abcde"
// As length of s2 is 5 so we will check in s1 till length where 5
// character can be adjusted so we will check till 10 - 5 + 1 = 6 so
// index will be 1 less than 6 which will be 5. So, we will check till C
// which has index 5.
for(int i=0; i<s1.length()-s2.length()+1; i++)
{
checkSS = false;
  
if(s1.charAt(i) == s2.charAt(0))
{
for(int j=0; j<s2.length(); j++)
{
if(s1.charAt(i+j) == s2.charAt(j))
checkSS = true; // keep assigning it true if characters are matching.
else
{
// if one of the characters doesn't match then change checkSS to false
// and break the loop as there is no need to compare it further.
checkSS = false;
break;
}
}
}
  
// if checkSS becomes true means we already find that s2 is substring of s1
// so just break the outer loop. No need to traverse the whole string.
if(checkSS)
break;
}
  
// Just return the checkSS value.
return checkSS;
}
  
public static void main(String []args)
{
String s1, s2; // Define the strings.
  
Scanner sc = new Scanner(System.in); // For input.
  
// For inputting String s1.
System.out.println("Enter String s1: ");
s1 = sc.nextLine();
  
// For inputting String s2.
System.out.println("Enter String s2: ");
s2 = sc.nextLine();
  
// if method returns true then print it is a substring otherwise not.
if(checkSubString(s1,s2))
System.out.println("s2 is a substring of s1.");
else
System.out.println("s2 is not a substring of s1.");
  
}
}

CODE Screenshots:

OUTPUT Screenshots:

(Note: On left are the s1 and s2 and right side contains the output.)