Java Utililty Methods String Case Swap

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

if (isEmpty(str)) {
    return str;
final char[] buffer = str.toCharArray();
boolean whitespace = true;
for (int i = 0; i < buffer.length; i++) {
    final char ch = buffer[i];
    if (Character.isUpperCase(ch)) {
...

Swaps the case of String.

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

null is returned as null.

if (str == null) {
    return null;
int sz = str.length();
StringBuilder buffer = new StringBuilder(sz);
boolean whitespace = false;
char ch;
char tmp;
...

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

• Upper case character converts to Lower case
• Title case character converts to Lower case
• Lower case character after Whitespace or at start converts to Title case
• Other Lower case character converts to Upper case

Whitespace is defined by Character#isWhitespace(char) .

char[] buffer = str.toCharArray();
boolean whitespace = true;
for (int i = 0; i < buffer.length; i++) {
    char ch = buffer[i];
    if (Character.isUpperCase(ch)) {
        buffer[i] = Character.toLowerCase(ch);
        whitespace = false;
    } else if (Character.isTitleCase(ch)) {
...

int strLen;
if (str == null || (strLen = str.length()) == 0) {
    return str;
StringBuilder buffer = new StringBuilder(strLen);
char ch = 0;
for (int i = 0; i < strLen; i++) {
    ch = str.charAt(i);
...

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) .

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);
...

int strLen;
if ((str == null) || ((strLen = str.length()) == 0)) {
    return str;
StringBuffer buffer = new StringBuffer(strLen);
char ch = '\000';
for (int i = 0; i < strLen; i++) {
    ch = str.charAt(i);
...

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

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;
...

 StringUtil.trim('Password') = 'password' StringUtil.trim('password') = 'Password' 

StringBuffer sbuf = new StringBuffer(str);
sbuf.deleteCharAt(0);
if (Character.isLowerCase(str.substring(0, 1).toCharArray()[0])) {
    sbuf.insert(0, str.substring(0, 1).toUpperCase());
} else {
    sbuf.insert(0, str.substring(0, 1).toLowerCase());
return sbuf.toString();
...