Java String Case Swap swapCase(String str)

Description

Swaps the case of a String using a word based algorithm.

License

Open Source License

Parameter

Parameter	Description
str	the String to swap case, may be null

Return

the changed String, null if null String input

Declaration

public static String swapCase(String str) 

Method Source Code

//package com.java2s;
//License from project: Open Source License 

public class Main {
    /**//from   w  w  w  . j a v a  2  s .co m
     * <p>
     * Swaps the case of a String using a word based algorithm.
     * </p>
     * 
     * <ul>
     * <li>Upper case character converts to Lower case</li>
     * <li>Title case character converts to Lower case</li>
     * <li>Lower case character after Whitespace or at start converts to Title
     * case</li>
     * <li>Other Lower case character converts to Upper case</li>
     * </ul>
     * 
     * <p>
     * Whitespace is defined by {@link Character#isWhitespace(char)}. A
     * <code>null</code> input String returns <code>null</code>.
     * </p>
     * 
     * <pre>
     * StringUtils.swapCase(null)                 = null
     * StringUtils.swapCase("")                   = ""
     * StringUtils.swapCase("The dog has a BONE") = "tHE DOG HAS A bone"
     * </pre>
     * 
     * @param str
     *            the String to swap case, may be null
     * @return the changed String, <code>null</code> if null String input
     */
    public static String swapCase(String str) {
        int strLen;
        if (str == null || (strLen = str.length()) == 0) {
            return str;
        }
        StringBuilder buffer = new StringBuilder(strLen);

        boolean whitespace = true;
        char ch = 0;
        char tmp = 0;

        for (int i = 0; i < strLen; i++) {
            ch = str.charAt(i);
            if (Character.isUpperCase(ch)) {
                tmp = Character.toLowerCase(ch);
            } else if (Character.isTitleCase(ch)) {
                tmp = Character.toLowerCase(ch);
            } else if (Character.isLowerCase(ch)) {
                if (whitespace) {
                    tmp = Character.toTitleCase(ch);
                } else {
                    tmp = Character.toUpperCase(ch);
                }
            } else {
                tmp = ch;
            }
            buffer.append(tmp);
            whitespace = Character.isWhitespace(ch);
        }
        return buffer.toString();
    }
}

Related

1. swapCase(final String str)
2. swapCase(String str)
3. swapCase(String str)
4. swapCase(String str)
5. swapCase(String str)
6. swapCase(String str)
7. swapFirstLetterCase(String str)