Pra quem duvida, eis a implementação dos métodos contains e indexOf:
/**
* Returns true if and only if this string contains the specified
* sequence of char values.
*
* @param s the sequence to search for
* @return true if this string contains <code>s</code>, false otherwise
* @throws NullPointerException if <code>s</code> is <code>null</code>
* @since 1.5
*/
public boolean contains(CharSequence s) {
return indexOf(s.toString()) > -1;
}
/**
* Returns the index within this string of the first occurrence of the
* specified substring. The integer returned is the smallest value
* <i>k</i> such that:
* <blockquote><pre>
* this.startsWith(str, <i>k</i>)
* </pre></blockquote>
* is <code>true</code>.
*
* @param str any string.
* @return if the string argument occurs as a substring within this
* object, then the index of the first character of the first
* such substring is returned; if it does not occur as a
* substring, <code>-1</code> is returned.
*/
public int indexOf(String str) {
return indexOf(str, 0);
}
/**
* Returns the index within this string of the first occurrence of the
* specified substring, starting at the specified index. The integer
* returned is the smallest value <tt>k</tt> for which:
* <blockquote><pre>
* k >= Math.min(fromIndex, this.length()) && this.startsWith(str, k)
* </pre></blockquote>
* If no such value of <i>k</i> exists, then -1 is returned.
*
* @param str the substring for which to search.
* @param fromIndex the index from which to start the search.
* @return the index within this string of the first occurrence of the
* specified substring, starting at the specified index.
*/
public int indexOf(String str, int fromIndex) {
return indexOf(value, offset, count,
str.value, str.offset, str.count, fromIndex);
}
Finalmente, aqui está o for escondido:
[code] /**
* Code shared by String and StringBuffer to do searches. The
* source is the character array being searched, and the target
* is the string being searched for.
*
* @param source the characters being searched.
* @param sourceOffset offset of the source string.
* @param sourceCount count of the source string.
* @param target the characters being searched for.
* @param targetOffset offset of the target string.
* @param targetCount count of the target string.
* @param fromIndex the index to begin searching from.
*/
static int indexOf(char[] source, int sourceOffset, int sourceCount,
char[] target, int targetOffset, int targetCount,
int fromIndex) {
if (fromIndex >= sourceCount) {
return (targetCount == 0 ? sourceCount : -1);
}
if (fromIndex < 0) {
fromIndex = 0;
}
if (targetCount == 0) {
return fromIndex;
}
char first = target[targetOffset];
int max = sourceOffset + (sourceCount - targetCount);
for (int i = sourceOffset + fromIndex; i <= max; i++) {
/* Look for first character. */
if (source[i] != first) {
while (++i <= max && source[i] != first);
}
/* Found first character, now look at the rest of v2 */
if (i <= max) {
int j = i + 1;
int end = j + targetCount - 1;
for (int k = targetOffset + 1; j < end && source[j] ==
target[k]; j++, k++);
if (j == end) {
/* Found whole string. */
return i - sourceOffset;
}
}
}
return -1;
}[/code]
