How can I efficiently replace multiple substrings in a string using Java?

Replacing Multiple Substrings in a String: An Efficient Approach

Replacing multiple substrings in a string can be a common task in various programming scenarios. While using String.replace repeatedly for each substring may seem straightforward, it can be inefficient for large strings or when dealing with many replacement pairs.

To overcome this limitation, a more efficient approach involves leveraging the java.util.regex.Matcher class, which allows for the efficient replacement of multiple substrings using regular expressions.

The following steps outline how to use Matcher for substring replacement:

1. Create a map containing the substring (key) and its replacement (value) pairs.
2. Compose a regular expression pattern that matches the substrings with alternates.
3. Create a Matcher by compiling the pattern.
4. Use the Matcher to search for matches in the input string.
5. Append the replacement text to a StringBuffer during the match iteration.
6. Append any remaining text after the last match.

An example of this approach is provided below, replacing multiple tokens from a map in a given string:

<code class="java">Map<String, String> tokens = new HashMap<>();
tokens.put("cat", "Garfield");
tokens.put("beverage", "coffee");

String template = "%cat% really needs some %beverage%.";

// Create pattern of the format "%(cat|beverage)%"
String patternString = "%(" + StringUtils.join(tokens.keySet(), "|") + ")%";
Pattern pattern = Pattern.compile(patternString);
Matcher matcher = pattern.matcher(template);

StringBuffer sb = new StringBuffer();
while (matcher.find()) {
    matcher.appendReplacement(sb, tokens.get(matcher.group(1)));
}
matcher.appendTail(sb);

System.out.println(sb.toString());</code>

By using Matcher, the compilation of the regular expression is done once, and the matching and replacement process is performed efficiently for the input string, providing a significant performance advantage, especially when dealing with large or multiple strings.

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