Java Utililty Methods String Substritute

StringBuilder ret = new StringBuilder(input.length());
int start = 0;
int index = -1;
final int length = pattern.length();
while ((index = input.indexOf(pattern, start)) >= start) {
    ret.append(input.substring(start, index));
    ret.append(sub);
    start = index + length;
...

substitute returns a string in which 'find' is substituted by 'newString'

if (in == null || find == null || newString == null)
    return in;
char[] working = in.toCharArray();
StringBuffer stringBuffer = new StringBuffer();
int startindex = in.indexOf(find);
if (startindex < 0)
    return in;
int currindex = 0;
...

String s = original;
int pos;
while (0 <= (pos = s.indexOf(match))) {
    StringBuilder sb = new StringBuilder(s);
    s = sb.replace(pos, pos + match.length(), subst).toString();
return s;

if (s == null || from == null || s.equals("") || from.equals("")) {
    return s;
String res = "";
int ind = s.indexOf(from);
while (ind >= 0) {
    res += s.substring(0, ind);
    res += to;
...

StringBuilder buffer = new StringBuilder(str.length() + 32);
int index = 0;
while (index < str.length()) {
    int startIndex = index;
    index = str.indexOf(SUBSTITUTION_PLACEHOLDER_PREFIX_CHAR, index);
    if (index < 0)
        index = str.length();
    if (index > startIndex)
...

if (from == null || from.equals("") || to == null)
    return str;
int index = str.indexOf(from);
if (index == -1)
    return str;
StringBuilder buf = new StringBuilder(str.length());
int lastIndex = 0;
while (index != -1) {
...

int index = str.indexOf(source);
if (index == -1) 
    return str;
int start = index, end = index + source.length();
return str.substring(0, start) + target + str.substring(end);

int index = str.indexOf(source);
if (index == -1) 
    return str;
int start = index, end = index + source.length();
return str.substring(0, start) + target + str.substring(end);

int subsLeftToPreform = num;
StringBuffer buf = new StringBuffer(str);
int ind = str.indexOf(variable);
while (ind >= 0 && subsLeftToPreform-- != 0) {
    buf.replace(ind, ind + variable.length(), value);
    ind = buf.toString().indexOf(variable);
return buf.toString();
...

int start = string.indexOf(pattern);
while (start != -1) {
    StringBuffer buffer = new StringBuffer(string);
    buffer.delete(start, start + pattern.length());
    buffer.insert(start, replacement);
    string = new String(buffer);
    start = string.indexOf(pattern, start + replacement.length());
return string;