Split a String into a Number of Substrings in Java (original) (raw)

Last Updated : 17 Feb, 2022

Given a String, the task it to split the String into a number of substrings.

A String in java can be of 0 or more characters.

Examples :

(a) "" is a String in java with 0 character (b) "d" is a String in java with 1 character (c) "This is a sentence." is a string with 19 characters.

Substring: A String that is a part of another string is called substring of the other string.

Example 1: Let us consider the string bat. The possible substrings are:

(1) "b" (2) "ba" (3) "bat", every string is a substring of itself (4) "a" (5) "at" (6) "t" (7) "" , "" is a substring of every string

Example 2: Let us consider the string The Cat. The possible substrings are:

(1) "T" (2) "Th" (3) "The" (4) "The " (5) "The C" (6) "The Ca" (7) "The Cat", every string is a substring of itself (8) "h" (9) "he" (10) "he " (11) "he C" (12) "he Ca" (13) "he Cat" (14) "e" (15) "e " (16) "e C" (17) "e Ca" (18) "e Cat" (19) " " (20) " C" (21) " Ca" (22) " Cat" (23) "C" (24) "Ca" (25) "Cat" (26) "a" (27) "at" (28) "t" (29) "" , "" is a substring of every string

Note: Totalnumber of substrings of a string of length N is (N * (N + 1)) / 2. This is after excluding the empty string “” because it is a substring of all strings.

Approach:

Let us consider a string which has n characters:

For each character at index i (0 to n-1): find substrings of length 1, 2, ..., n-i

Example: Let our string be cat, here n = 3 (the length of string) here, index of 'c' is 0 index of 'a' is 1 index of 't' is 2

Loop from i = 0 to 2: (since n-1 = 2)

When i = 0: Substring of length 1 : "c"
Substring of length 2 : "ca" Substring of length 3 : "cat" , (substring of length n-i or 3-0 = 3)

When i = 1: Substring of length 1 : "a" Substring of length 2 : "at" , (substring of length n-i or 3-1 = 2)

When i = 2: Substring of length 1 : "t" , (substring of length n-i or 3-2 = 1)

Example:

Java

import java.io.*;

import java.util.ArrayList;

class SubstringsOfAString {

`` public static ArrayList<String>

`` splitSubstrings(String s)

`` {

`` int i, j;

`` int stringLength = s.length();

`` ArrayList<String> subStringList

`` = new ArrayList<String>();

`` for (i = 0 ; i < stringLength; i++) {

`` for (j = i + 1 ; j <= stringLength; j++) {

`` subStringList.add(s.substring(i, j));

`` }

`` return subStringList;

`` }

`` public static void main(String[] args)

`` {

`` String stringInput = new String( "The Cat" );

`` ArrayList<String> subStringList

`` = SubstringsOfAString.splitSubstrings(

`` stringInput);

`` System.out.println(

`` "\nSubstring list printed as an ArrayList : " );

`` System.out.println(subStringList);

`` System.out.println(

`` "\n\nAll substrings printed 1 per line : " );

`` int count = 1 ;

`` for (String it : subStringList) {

`` System.out.println( "(" + count + ") \"" + it

`` + "\"" );

`` count++;

`` }

}

Output

Substring list printed as an ArrayList : [T, Th, The, The , The C, The Ca, The Cat, h, he, he , he C, he Ca, he Cat, e, e , e C, e Ca, e Cat, , C, Ca, Cat, C, Ca, Cat, a, at, t]

All substrings printed 1 per line : (1) "T" (2) "Th" (3) "The" (4) "The " (5) "The C" (6) "The Ca" (7) "The Cat" (8) "h" (9) "he" (10) "he " (11) "he C" (12) "he Ca" (13) "he Cat" (14) "e" (15) "e " (16) "e C" (17) "e Ca" (18) "e Cat" (19) " " (20) " C" (21) " Ca" (22) " Cat" (23) "C" (24) "Ca" (25) "Cat" (26) "a" (27) "at" (28) "t"

Time Complexity: O(n2) where n is the length of a string

Output 1: When string Input = bat

Substring list printed as an ArrayList : [b, ba, bat, a, at, t]

All substrings printed 1 per line : (1) "b" (2) "ba" (3) "bat" (4) "a" (5) "at" (6) "t"

Output 2: When string Input = The Cat

Substring list printed as an ArrayList : [T, Th, The, The , The C, The Ca, The Cat, h, he, he , he C, he Ca, he Cat, e, e , e C, e Ca, e Cat, , C, Ca, Cat, C, Ca, Cat, a, at, t]