How to Find Substrings in a String

Definition of substring

A sequence of consecutive characters within a larger string.

In other words, it is a smaller string that is written without changing the order of the characters selected from the original string or skipping any characters in the middle.

Example of substrings

Substrings of "abc": "", "a", "b", "c", "ab", "bc", "abc"

In mathematics, the empty string ("") is also considered a substring.

However, in programming problems, whitespace characters are usually not considered as substrings.

How to find substrings

Example

public static int countSubstring(String str) {
    int n = str.length();
    return n*(n+1)/2;
}