some smart code

UtilCodeGist.java

// shift a char
s[i] = (s[i] - 'a' + shift) % 26 + 'a';

// flip upper to lower alphabeta or vice versa
// ascii code 'A': 65, 'a': 97
// 97 - 32 = 65, flip 5th binary bit means minus or plus 32
// bitwise XOR can flip to opposite bit: 1 ^ 1 = 0, 1 ^ 0 = 1, 
s[i] ^= 32;
s[i] ^= 1 << 5;

// reg find 
// condition "A.*A|LLL" , count of 'A' > 1 or count of continuous 'L' > 2
// find() will find anyplace in s meet condition "A.*A|LLL"
Pattern.compile("A.*A|LLL").matcher(s).find();
// match() method check the whole string s match
Pattern.compile("A.*A|LLL").matcher(s).match();
// lookingAt() match prefix
Pattern.compile("A.*A|LLL").matcher(s).lookingAt();