Question

use java recursion

find # of times a substring is in a string but it has to be the exact same, no extra letters attached to it and capitalization matters.

input is 2 strings, output is an int

input: ("Hello it is hello it's me hellos" + "hi hellllloooo hi hello" + "hello", "hello")

should output: 3

input: (" Hello it is hello it's me hellos" + "hi hellllloooo hi hello" + "hello", "Hello")

should output: 1

input: (" Hello it is hello it's me hellos" + "hi hellllloooo hi hello" + "hello Hello ", "Hello")

should output: 2

input: (" HELLO it is hello it's me hellos" + "hi hellllloooo hi hello" + "hello Hello", "Hello")

should output: 1

input: (" HELLO it is hello it's me hellos" + "hi hellllloooo hi hello" + "hello Hello", "")

should output: 0

Answer 1

public class SubstringRecursion {

        public static void main(String[] args) {
                
                int times;
                times = substring("Hello World Welcome to new World","",0);
                System.out.println(times);
                times = substring("king of Kings","king",0);
                System.out.println(times);
                
                String s = "I felt happy because I saw the others were happy and because I knew I should feel happy, but I wasn’t really happy";
                times = substring(s, "happy", 0);
                System.out.println(times);

        }
        
        
        public static int substring(String string, String substring, int index) {
                
                if(substring.length()==0||string.length()==0)
                        return 0;
                // if it has no matching then return 0
                if(string.indexOf(substring)== -1) {
                        return 0;
                }
                
                // if string found we have to start checking from next character
                int i = string.indexOf(substring)+1;
                
                // adding 1 to new substring check
                return 1 + substring(string.substring(i), substring, index + 1);
        }
        

}

Code

Output