Java String Case Swap swapCase(String str)

Description

Swaps the case of a String changing upper and title case to lower case, and lower case to upper case.

Upper case character converts to Lower case
Title case character converts to Lower case
Lower case character converts to Upper case

For a word based algorithm, see WordUtils#swapCase(String) .

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;

public class Main {
    /**//w  w  w  . j  a v  a2s  . c  o  m
     * <p>Swaps the case of a String changing upper and title case to
     * lower case, and lower case to upper case.</p>
     *
     * <ul>
     *  <li>Upper case character converts to Lower case</li>
     *  <li>Title case character converts to Lower case</li>
     *  <li>Lower case character converts to Upper case</li>
     * </ul>
     *
     * <p>For a word based algorithm, see {@link WordUtils#swapCase(String)}.
     * 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>
     *
     * <p>NOTE: This method changed in Lang version 2.0.
     * It no longer performs a word based algorithm.
     * If you only use ASCII, you will notice no change.
     * That functionality is available in WordUtils.</p>
     *
     * @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;
        }
        StringBuffer buffer = new StringBuffer(strLen);

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