Please help me with JAVA 8 solution with all test cases passing for below problem

Given a string S consisting of letters 'a' and 'b',return the minimum number of swaps needed to obtain a string with no instances of 3 identical consecutive letters. You are given a string S consisting of N letters 'a' and / or 'b'. In one move you can swap one letter for the other('a' for 'b' or 'b' for 'a'). write a function solution that,given such a string S,returns the minimum number of moves required to obtain a string containing no instances of 3 identica; consecutive letters.

Examples: 1.Given S = "baaaaa", the function should return 1. The string without 3 identical consecutive letters which can be obtained in one move is "baabaa".

2. Given S = "baaabbaabbba", the function should return 2.There are four valid strings obtainable in 2 ,pves.for example,"bbaabbaabbaa".

3.Given S = "baabab",the function should return 0.

Write an efficient algorithm for following assumptions: . N is an integer within the range[0..200,000]; . String S is made only of the characters "a" and/or "b".