Convert Char to String.

1. Use String.valueOf(char)
2. Use Character.toString(char)
   • Note: this method simply returns a call to String.valueOf(char)
3. Use string concatenation String s = "" + 'c'
   • Note: this compiles down to

   1	String s = new StringBuilder().append("").append('c').toString();

   • which is less efficient because StringBuilder is backed by char[] (over-allocated by StringBuilder() to 16) and this array will be copied to the resulting String. On the other hand, String.valueOf(char) wraps the char in a single-element array and passes it to the package private constructor String(char[], boolean), which avoids the array copy.¹