Java Array vs String: Key Differences, Performance & When to Use
A Java Array is a fixed-length container of primitives or objects; a String is an immutable sequence of UTF-16 characters. Arrays are mutable, can be resized only by creating a new one; Strings never change once created.
Beginners often confuse them because both hold “characters” and both use square brackets in code. Arrays feel like “text I can edit,” Strings look like “text I can read,” so they assume interchangeable behavior.
Key Differences
Arrays store any type (int, char, custom objects), are mutable, and use length field. Strings store only characters, are immutable, and use length() method. Array access is O(1); String concatenation in loops creates new objects, hurting performance.
Which One Should You Choose?
Use an Array when you need to change elements or store non-text data. Pick String when the text is final or you’ll use built-in methods like substring, replace. For mutable text, prefer StringBuilder over either.
Can I convert a char[] to String quickly?
Yes, use new String(charArray). It copies the array; changes to the original array won’t affect the String.
Does String += in loops hurt performance?
Absolutely. Each += creates a new String object. Switch to StringBuilder or pre-sized char[] for speed.