How to Efficiently Replace Multiple Substrings in a Java String?

Efficient String Substitution in Java

Replacing multiple substrings in a string efficiently is a common task in programming. While the brute-force approach of using String.replace() for each substitution is straightforward, it can be inefficient, especially for large strings or when dealing with many replacements.

Replacing Substrings Using Regular Expressions

A more efficient solution involves using regular expressions. By compiling a pattern that matches all the desired substring replacements, you can replace multiple substrings at once.

Consider the following code example, which replaces tokens from a map within a template string using regular expressions:

<code class="java">import java.util.HashMap;
import java.util.Map;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

...

// Tokens to replace
Map<String, String> tokens = new HashMap<>();
tokens.put("cat", "Garfield");
tokens.put("beverage", "coffee");

// Template string with tokens
String template = "%cat% really needs some %beverage%.";

// Create pattern to match tokens
String patternString = "%(" + StringUtils.join(tokens.keySet(), "|") + ")%";
Pattern pattern = Pattern.compile(patternString);
Matcher matcher = pattern.matcher(template);

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

System.out.println(sb.toString()); // Prints the replaced string</code>

By using regular expressions, you can significantly improve the efficiency of multiple substring replacements, especially for large or complex input strings.

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