Search for the first word to be replaced. If it's in the string, recurse on the the part of the string before the occurrence, and on the part of the string after the occurrence.
Otherwise, continue with the next word to be replaced.
A naive implementation might look like this
public static String replaceAll(String input, String[] search, String[] replace) {
return replaceAll(input, search, replace, 0);
}
private static String replaceAll(String input, String[] search, String[] replace, int i) {
if (i == search.length) {
return input;
}
int j = input.indexOf(search[i]);
if (j == -1) {
return replaceAll(input, search, replace, i + 1);
}
return replaceAll(input.substring(0, j), search, replace, i + 1) +
replace[i] +
replaceAll(input.substring(j + search[i].length()), search, replace, i);
}
Sample usage:
String input = "Once upon a baz, there was a foo and a bar.";
String[] search = new String[] { "foo", "bar", "baz" };
String[] replace = new String[] { "bar", "baz", "foo" };
System.out.println(replaceAll(input, search, replace));
Output:
Once upon a foo, there was a bar and a baz.
A less-naive version:
public static String replaceAll(String input, String[] search, String[] replace) {
StringBuilder sb = new StringBuilder();
replaceAll(sb, input, 0, input.length(), search, replace, 0);
return sb.toString();
}
private static void replaceAll(StringBuilder sb, String input, int start, int end, String[] search, String[] replace, int i) {
while (i < search.length && start < end) {
int j = indexOf(input, search[i], start, end);
if (j == -1) {
i++;
} else {
replaceAll(sb, input, start, j, search, replace, i + 1);
sb.append(replace[i]);
start = j + search[i].length();
}
}
sb.append(input, start, end);
}
Unfortunately, Java's String has no indexOf(String str, int fromIndex, int toIndex) method. I've omitted the implementation of indexOf here as I'm not certain it's correct, but it can be found on ideone, along with some rough timings of various solutions posted here.
