How to Efficiently Replace Multiple Substrings in Java?

Replacing Multiple Substrings Efficiently in Java

Replacing multiple substrings within a string is necessary for various purposes. While the conventional string.replace method can suffice for simple cases, it might be insufficient for handling extensive strings or numerous replacements.

An efficient approach to tackle this issue is to leverage the java.util.regex.Matcher class. This requires some initial compilation time, but proves beneficial for large inputs or repetitive search patterns.

Consider the following scenario:

Problem: Replace multiple tokens (e.g., "cat" and "beverage") with their corresponding values (e.g., "Garfield" and "coffee") within a given string.

Solution:

1. Create a Map to store the substitution tokens.
2. Construct a pattern string using the tokens' keys.
3. Compile the pattern to create a Matcher instance.
4. Use the Matcher to process the input string.
5. Append the replacements to a StringBuffer.

<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 utilizing this approach, the initial compilation cost outweighs its benefits for small input sizes or frequently changing search patterns. However, it significantly improves efficiency when working with extensive strings or numerous replacements.

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