Splitting Strings in Java: Mastering split() and StringTokenizer

Splitting strings is a common task in Java — whether you're processing CSV files, parsing user input, or breaking down URLs. Java provides two primary tools for this: String.split() and StringTokenizer.

This tutorial explores both, highlighting their syntax, use cases, differences, performance, and best practices.

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🔍 What Is String Splitting?

String splitting means breaking a single string into multiple substrings based on a delimiter (e.g., comma, space, pipe).

Example:
"apple,banana,grape" → ["apple", "banana", "grape"]

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🛠 Using split() Method

Syntax

String[] parts = str.split(String regex);

Example

String fruits = "apple,banana,grape";
String[] result = fruits.split(",");
System.out.println(Arrays.toString(result)); // [apple, banana, grape]

With Limit

String[] result = fruits.split(",", 2);
// Output: [apple, banana,grape]

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🔎 Using StringTokenizer (Legacy)

Syntax

StringTokenizer tokenizer = new StringTokenizer(str, delimiter);

Example

String input = "one,two,three";
StringTokenizer tokenizer = new StringTokenizer(input, ",");
while (tokenizer.hasMoreTokens()) {
    System.out.println(tokenizer.nextToken());
}

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📊 split() vs StringTokenizer Comparison

Feature	split()	StringTokenizer
Introduced In	Java 1.4	Java 1.0
Returns	Array of strings	Tokens via iterator
Based On	Regex	Delimiter string
Null-safe	✅ Yes	❌ Can throw NPE
Thread-safe	✅ Yes (immutable)	❌ No
Flexibility	✅ High (regex)	🚫 Limited
Preferred In Modern Code	✅ Yes	🚫 Legacy API

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⚙️ Real-World Use Cases

• CSV Parsing: split(",")
• Log File Analysis: split("\s+")
• Tokenizing User Input: StringTokenizer (legacy)
• URL Breakdown: split("/")

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⚠️ Edge Cases & Pitfalls

1. Splitting by special regex characters

String path = "C:\Users\John";
String[] parts = path.split("\\"); // Need to escape backslash

2. Trailing empty strings

String input = "a,b,c,,";
String[] tokens = input.split(",");
System.out.println(tokens.length); // 4 (last empty is removed)

Use split(",", -1) to retain all tokens.

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🔄 Refactoring Example

❌ Naive Manual Splitting

String line = "a,b,c";
int comma1 = line.indexOf(",");
int comma2 = line.indexOf(",", comma1 + 1);
String part1 = line.substring(0, comma1);
String part2 = line.substring(comma1 + 1, comma2);

✅ Better with split()

String[] parts = line.split(",");

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📌 What's New in Java Strings?

Java 11

• Added isBlank(), lines(), strip(), etc.
• split() enhanced with better Unicode handling

Java 13+

• Text Blocks (multi-line strings)

Java 21

• String Templates (preview feature)

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✅ Best Practices

• Prefer split() over StringTokenizer in modern code
• Escape regex characters properly (\. for period, \\ for backslash)
• Use limit argument if you want to control splits
• Use split(",", -1) to preserve empty tokens
• Avoid using StringTokenizer unless maintaining legacy systems

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🔚 Conclusion and Key Takeaways

• Use split() for modern, flexible, regex-based string splitting.
• StringTokenizer is a legacy class — avoid unless necessary.
• Always consider edge cases like empty strings, special characters, or multiple delimiters.
• Proper string splitting leads to cleaner, more maintainable code.

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❓ FAQ

1. What’s the main difference between split() and StringTokenizer?

split() uses regex and returns an array. StringTokenizer is legacy and returns tokens one by one.

2. When should I use StringTokenizer?

Only in legacy code or where minimal dependencies are needed.

3. How to retain empty tokens?

Use split(delimiter, -1).

4. Can split() handle regex?

Yes. It's fully regex-based.

5. Is StringTokenizer thread-safe?

No. split() is safer due to immutability.

6. How to split by whitespace?

Use split("\s+").

7. How to split a string into characters?

Use split("") or convert to char array.

8. What if delimiter is a special regex character?

Escape it with \.

9. Is split() faster than StringTokenizer?

Generally yes, and much more flexible.

10. Can I use multiple delimiters?

Yes. Use regex like split("[,;|]").