Java - Write code to Capitalizes a String changing the first letter to title case as per Character#toTitleCase(char)

Requirements

Write code to Capitalizes a String changing the first letter to title case as per Character#toTitleCase(char)

capitalize(null)  = null
capitalize("")    = ""
capitalize("cat") = "Cat"
capitalize("cAt") = "CAt"

Hint

Use Character.toTitleCase() method

Demo

//package com.book2s;

public class Main {
    public static void main(String[] argv) {
        String str = "book2s.com";
        System.out.println(capitalize(str));
    }// w ww. ja v a 2  s  .  c  o m

    /**
     * <p>
     * Capitalizes a String changing the first letter to title case as per
     * {@link Character#toTitleCase(char)}. No other letters are changed.
     * </p>
     * 
     * <pre>
     * capitalize(null)  = null
     * capitalize("")    = ""
     * capitalize("cat") = "Cat"
     * capitalize("cAt") = "CAt"
     * </pre>
     * 
     * @param str
     *            the String to capitalize, may be null
     * @return the capitalized String, <code>null</code> if null String input
     * @see #uncapitalize(String)
     * @since 2.0
     */
    public static String capitalize(String str) {
        if (str == null) {
            return null;
        }
        StringBuilder result = new StringBuilder(str.toString());
        if (result.length() > 0) {
            result.setCharAt(0, Character.toTitleCase(result.charAt(0)));
        }
        return result.toString();

    }
}