String 经常用法最优算法实现总结 （一）

<pre name="code" class="java"><span style="font-family: Arial, Helvetica, sans-serif;"></pre><p>1. reverse</p><p><pre name="code" class="java">   /**</span>

     * @Description: reverse a string.
     * @param str the String to reverse, may be null
     * @return reversedStr the reversed String, null if null String input
     */
    public static String reverse(String str) {
        if (isEmpty(str)) {
            return str;
        }

        return new StringBuilder(str).reverse().toString();
    }

    /**
     * @Description: Removes all occurrences of a substring from within the source string.
     * @param str the source String to search
     * @param remove the String to search for and remove
     * @return the substring with the string removed if found, null if null String input
     */
    public static String remove(String str, String remove) {
        if (isEmpty(str) || isEmpty(remove)) {
            return str;
        }

        return str.replace(remove, "");
    }

    /**
     * 
     * @Title: startsWithIgnoreCase
     * @Description: check if a string starts with a specified prefix.
     * @param str input value
     * @param prefix prefix value
     * @return true if the string starts with the prefix, case insensitive, or both null, blank
     */
    public static boolean startsWithIgnoreCase(String str, String prefix) {
        if (str == null || prefix == null) {
            return (str == null && prefix == null);
        }

        if (prefix.length() > str.length()) {
            return false;
        }

        return str.toUpperCase().startsWith(prefix.toUpperCase());
    }

   /**
     * whether value does not contain number(s).
     * 
     * @Title: isAllAlphas
     * @param value the source to be handled
     * @return boolean
     */
    public static boolean isAllAlphas(String value) {
        // if input parameter is null, just return
        if (value == null) {
            return false;
        }

        for (int i = 0; i < value.length(); i++) {
            if (!(Character.isLetter(value.charAt(i)))) {
                return false;
            }
        }

        return true;
    }

  /**
     * check if the CharSequence contains only unicode digits.
     * 
     * @Title: isNumber
     * @param str input str
     * @return true or false
     */
    public static boolean isNumeric(String str) {
        // if input parameter is null, just return false
        if (isEmpty(str)) {
            return false;
        }

        for (int i = 0; i < str.length(); i++) {
            // if there is a alpha, return false
            if (!Character.isDigit(str.charAt(i))) {
                return false;
            }
        }
        
        return true;
    }