Why String Is Non-Primitive Data Type in Java?


Scott Campbell

The String class in Java is a non-primitive data type, which means it is not one of the eight built-in data types (boolean, byte, char, short, int, long, float, double). Instead, it is a class that belongs to the java.lang package and provides a way to represent and manipulate sequences of characters.

String as an Object

Being a class-based object in Java, strings have several advantages over primitive data types. One of the key benefits is that strings can be easily manipulated using various methods provided by the String class. These methods allow you to perform operations such as concatenation, searching for substrings, replacing characters or substrings, and many more.

Let’s explore some reasons why string is a non-primitive data type:

1. Dynamic Length

A string can have a variable length. Unlike primitive data types that have fixed sizes in memory (such as int takes 4 bytes), a string’s length can vary depending on the number of characters it contains. This flexibility allows you to store and manipulate text of any length without worrying about memory limitations.

2. Immutability

In Java, strings are immutable objects. This means that once a string object is created with its initial value, it cannot be changed.

When you perform operations on strings (e.g., concatenation), new string objects are created instead of modifying the original ones. This immutability provides several benefits such as thread-safety and efficient memory utilization.

3. String Pool

The Java platform maintains a special memory area called the “string pool” to optimize memory usage for strings. When you create a string object using double quotes (“..”), Java checks if an equivalent string already exists in the pool.

If it does, the existing string is returned instead of creating a new object. This mechanism helps reduce memory overhead when multiple strings with the same value are used in a program.

4. Garbage Collection

Being objects, strings are subject to automatic garbage collection in Java. When a string object is no longer referenced by any part of the program, it becomes eligible for garbage collection and its memory is reclaimed by the JVM. This automatic memory management eliminates the need for manual memory deallocation and reduces the risk of memory leaks.


In summary, strings being non-primitive data types in Java provide numerous benefits in terms of flexibility, immutability, efficient memory usage through string pooling, and automatic garbage collection. These features make strings a powerful tool for handling textual data in Java applications.

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