Java Program to print all substrings of a given string

Program

import java.util.Scanner;
public class SubstringsOfString {
    public String[] getSubstrings(String string)
    {
        int len = string.length();  
        int temp = 0;  
        String arrSubset[] = new String[len*(len+1)/2]; 
        for(int i = 0; i < len; i++) {  
            for(int j = i; j < len; j++) {  
                arrSubset[temp] = string.substring(i, j+1);  
                temp++;  
            }  
        }
        return arrSubset; 
    }
    public static void main(String[] args){
        SubstringsOfString substringsOfString = new SubstringsOfString();
        Scanner reader = new Scanner(System.in);
        System.out.print("Enter a string to get all substrings: ");
        String enteredString = reader.nextLine();
        String subsets[] = substringsOfString.getSubstrings(enteredString);
        System.out.println("Substring of a given String are ");  
        for(int i = 0; i < subsets.length; i++) {  
            System.out.println(subsets[i]);  
        }                
    }
}

This program generates and prints all substrings of a given string.

1. Input:

   • The program prompts the user to enter a string.

2. Logic:

   • A substring is a contiguous sequence of characters within a string.
   • For a string of length n, there are n*(n+1)/2 substrings.
   • Example:
     • For "abc":
       • Substrings: "a", "b", "c", "ab", "bc", "abc".

3. Steps:

   • Calculate the total number of substrings (n*(n+1)/2) and initialize an array arrSubset to store them.
   • Use two nested loops:
     • Outer loop: Fix the starting point of the substring (i).
     • Inner loop: Fix the ending point (j).
     • Extract the substring using substring(i, j+1).
   • Add each substring to the array.

4. Output:

   • Iterate through the array and print all stored substrings.

5. Key Methods:

   • substring(start, end): Returns a substring from index start to end-1.
   • Dynamic Array Indexing: The variable temp is used to track the position in the arrSubset array.

6. Example Execution:

   • Input:

     Enter a string to get all substrings: abc
     

   • Process:
     • Substrings generated:
       • "a", "b", "c", "ab", "bc", "abc"
   • Output:

     Substring of a given String are 
     a
     b
     c
     ab
     bc
     abc
     

7. Complexity:

   • Time Complexity: O(n²) due to the nested loops.
   • Space Complexity: O(n²) for storing substrings.

Features:

• Flexible Input:
  • Works for any string, including alphanumeric and special characters.
• Array Storage:
  • Allows access to all substrings for further processing.

Use Case:

• Text analysis, such as finding patterns or matches.
• Educational purposes to understand substring generation logic.

Output

$ javac SubstringsOfString.java
$ java SubstringsOfString
Enter a string to get all substrings: World
Substring of a given String are
W
Wo
Wor
Worl
World
o
or
orl
orld
r
rl
rld
l
ld
d