Java String Case Swap swapCase(String str)

Description

Swaps the case of String.

Properly looks after making sure the start of words are Titlecase and not Uppercase.

null is returned as null.

License

Apache License

Parameter

Parameter	Description
str	the String to swap the case of

Return

the modified String

Declaration

public static String swapCase(String str) 

Method Source Code

//package com.java2s;
/* ====================================================================
 * The Apache Software License, Version 1.1
 *
 * Copyright (c) 2002 The Apache Software Foundation.  All rights
 * reserved./*from ww w . j av  a  2  s.  co m*/
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 *    any, must include the following acknowlegement:
 *       "This product includes software developed by the
 *        Apache Software Foundation (http://www.codehaus.org/)."
 *    Alternately, this acknowlegement may appear in the software itself,
 *    if and wherever such third-party acknowlegements normally appear.
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 *    Foundation" must not be used to endorse or promote products derived
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 * 5. Products derived from this software may not be called "Apache"
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 * This software consists of voluntary contributions made by many
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public class Main {
    /**
     * <p>Swaps the case of String.</p>
     *
     * <p>Properly looks after making sure the start of words
     * are Titlecase and not Uppercase.</p>
     *
     * <p><code>null</code> is returned as <code>null</code>.</p>
     *
     * @param str the String to swap the case of
     * @return the modified String
     */
    public static String swapCase(String str) {
        if (str == null) {
            return null;
        }
        int sz = str.length();
        StringBuilder buffer = new StringBuilder(sz);

        boolean whitespace = false;
        char ch;
        char tmp;

        for (int i = 0; i < sz; 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();
    }

    /**
     * <p>Checks if the String contains only whitespace.</p>
     *
     * <p><code>null</code> will return <code>false</code>. An
     * empty String will return <code>true</code>.</p>
     *
     * @param str the String to check
     * @return <code>true</code> if only contains whitespace, and is non-null
     */
    public static boolean isWhitespace(String str) {
        if (str == null) {
            return false;
        }
        int sz = str.length();
        for (int i = 0; i < sz; i++) {
            if ((Character.isWhitespace(str.charAt(i)) == false)) {
                return false;
            }
        }
        return true;
    }
}

Related

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