Question

Given the following method:

public boolean check(String s) {

return s.length() >= 2 &&

(s.charAt(0) == s.charAt(1) || check(s.substring(1))); }

This method will return true if and only if:

1. s.charAt(0) == s.charAt(1)

2. s starts with two or more of the same characters

3. s ends with two or more of the same characters

4. s contains two or more of the same characters

5. s contains two or more of the same character in a row

Answer 1

Given
public boolean check(String s) {
    return s.length() >= 2 && (s.charAt(0) == s.charAt(1) || check(s.substring(1)));
}

s.length() >= 2 means string length should be greater than or equals to 2

s.charAt(0) == s.charAt(1) means the first two characters of the string are same ot

check(s.substring(1)) is a recursive call doing same from string except the first character.
 
So, (s.charAt(0) == s.charAt(1) || check(s.substring(1)) checks for character match for the to adjacent characters in the string.

So, answer is "s contains two or more of the same character in a row"

s contains two or more of the same character in a row