Java String remove substring from start and end

//package com.demo2s;

public class Main {
    public static void main(String[] argv) throws Exception {
        String str = ".comdemo2s.com";
        System.out.println(strip(str,".com"));
    }/* w w w  . ja  v  a 2 s  . c om*/

    /**
     * The empty String <code>""</code>.
     * @since 2.0
     */
    public static final String EMPTY = "";


    /**
     * <p>Strips any of a set of characters from the start and end of a String.
     * This is similar to {@link String#trim()} but allows the characters
     * to be stripped to be controlled.</p>
     *
     * <p>A <code>null</code> input String returns <code>null</code>.
     * An empty string ("") input returns the empty string.</p>
     *
     * <p>If the stripChars String is <code>null</code>, whitespace is
     * stripped as defined by {@link Character#isWhitespace(char)}.
     * Alternatively use {@link #strip(String)}.</p>
     *
     * <pre>
     * strip(null, *)          = null
     * strip("", *)            = ""
     * strip("abc", null)      = "abc"
     * strip("  abc", null)    = "abc"
     * strip("abc  ", null)    = "abc"
     * strip(" abc ", null)    = "abc"
     * strip("  abcyx", "xyz") = "  abc"
     * </pre>
     *
     * @param str  the String to remove characters from, may be null
     * @param stripChars  the characters to remove, null treated as whitespace
     * @return the stripped String, <code>null</code> if null String input
     */
    public static String strip(String str, String stripChars) {
        if (isEmpty(str)) {
            return str;
        }
        str = stripStart(str, stripChars);
        return stripEnd(str, stripChars);
    }

    /**
     * <p>Checks if a String is empty ("") or null.</p>
     *
     * <pre>
     * isEmpty(null)      = true
     * isEmpty("")        = true
     * isEmpty(" ")       = false
     * isEmpty("bob")     = false
     * isEmpty("  bob  ") = false
     * </pre>
     *
     * <p>NOTE: This method changed in Lang version 2.0.
     * It no longer trims the String.
     * That functionality is available in isBlank().</p>
     *
     * @param str  the String to check, may be null
     * @return <code>true</code> if the String is empty or null
     */
    public static boolean isEmpty(String str) {
        return str == null || str.length() == 0;
    }

    /**
     * <p>Strips any of a set of characters from the start of a String.</p>
     *
     * <p>A <code>null</code> input String returns <code>null</code>.
     * An empty string ("") input returns the empty string.</p>
     *
     * <p>If the stripChars String is <code>null</code>, whitespace is
     * stripped as defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * stripStart(null, *)          = null
     * stripStart("", *)            = ""
     * stripStart("abc", "")        = "abc"
     * stripStart("abc", null)      = "abc"
     * stripStart("  abc", null)    = "abc"
     * stripStart("abc  ", null)    = "abc  "
     * stripStart(" abc ", null)    = "abc "
     * stripStart("yxabc  ", "xyz") = "abc  "
     * </pre>
     *
     * @param str  the String to remove characters from, may be null
     * @param stripChars  the characters to remove, null treated as whitespace
     * @return the stripped String, <code>null</code> if null String input
     */
    public static String stripStart(String str, String stripChars) {
        int strLen;
        if (str == null || (strLen = str.length()) == 0) {
            return str;
        }
        int start = 0;
        if (stripChars == null) {
            while ((start != strLen) && Character.isWhitespace(str.charAt(start))) {
                start++;
            }
        } else if (stripChars.length() == 0) {
            return str;
        } else {
            while ((start != strLen) && (stripChars.indexOf(str.charAt(start)) != -1)) {
                start++;
            }
        }
        return str.substring(start);
    }

    /**
     * <p>Strips any of a set of characters from the end of a String.</p>
     *
     * <p>A <code>null</code> input String returns <code>null</code>.
     * An empty string ("") input returns the empty string.</p>
     *
     * <p>If the stripChars String is <code>null</code>, whitespace is
     * stripped as defined by {@link Character#isWhitespace(char)}.</p>
     *
     * <pre>
     * stripEnd(null, *)          = null
     * stripEnd("", *)            = ""
     * stripEnd("abc", "")        = "abc"
     * stripEnd("abc", null)      = "abc"
     * stripEnd("  abc", null)    = "  abc"
     * stripEnd("abc  ", null)    = "abc"
     * stripEnd(" abc ", null)    = " abc"
     * stripEnd("  abcyx", "xyz") = "  abc"
     * </pre>
     *
     * @param str  the String to remove characters from, may be null
     * @param stripChars  the characters to remove, null treated as whitespace
     * @return the stripped String, <code>null</code> if null String input
     */
    public static String stripEnd(String str, String stripChars) {
        int end;
        if (str == null || (end = str.length()) == 0) {
            return str;
        }

        if (stripChars == null) {
            while ((end != 0) && Character.isWhitespace(str.charAt(end - 1))) {
                end--;
            }
        } else if (stripChars.length() == 0) {
            return str;
        } else {
            while ((end != 0) && (stripChars.indexOf(str.charAt(end - 1)) != -1)) {
                end--;
            }
        }
        return str.substring(0, end);
    }

}