How to Efficiently Iterate Through a String's Characters in Java?

Approaches for Iterating through a String's Characters in Java

String manipulation is essential in Java programming. One of the fundamental tasks involves iterating over the characters within a string. Various techniques exist for this purpose, including:

1. Using StringTokenizer: The StringTokenizer class can tokenize a string into smaller strings or tokens based on a specified delimiter. However, this approach has limitations in handling Unicode characters.
2. Converting String to char[] and Iterating: Another method is to convert the string into an array of characters (char[]) using the String.toCharArray() method. This allows for sequential iteration over the characters.

Recommended Approach

For simple and efficient iteration, the most preferred and correct way is to use a for loop along with the charAt() method:

String s = "...stuff...";

for (int i = 0; i < s.length(); i++) {
    char c = s.charAt(i);        
    // Process char
}

Considerations

This approach relies on the assumption that the characters in the string fall within the Basic Multilingual Plane (BMP) of Unicode. For characters outside the BMP, the charAt() method will return supplementary characters represented by surrogate pairs. If handling such characters is necessary, alternative approaches like Java 8's Stream API and code points manipulation should be considered.

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