Write a recursive method count Substrings that counts the number of non-overlapping occurrences of a string s2 in a string s1. Use the method indexOf() from String class.

As an example, with s1=abab and s2=ab, countSubstrings returns 2. With s1=aaabbaa and s2=aa, countSubstrings returns 2. With s1=aabbaa and s2=AA, countSubStrings returns 0.

Show the output on the following strings:

s1 = Java is a programming language originally developed by James Gosling at Sun Microsystems and released in 1995 as a core component of Sun Microsystems Java platform. The language derives much of its syntax from C and C++ but has a simpler object model and fewer low-level facilities. Java applications are typically compiled to bytecode (class file) that can run on any Java Virtual Machine (JVM) regardless of computer architecture. Java is a general-purpose, concurrent, class-based, object-oriented language that is specifically designed to have as few implementation dependencies as possible. Java is currently one of the most popular programming languages in use, particularly for client-server web applications, with a reported 10 million users. s2= Java.