Primitive vs Non-Primitive Data Type in Java
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Below is the deep comparison between Primitive Data Types and Non-Primitive Data Types.
- But i would suggest to first read the Primitive Data Types & Non-Primitive Data Types separately and then read below differences.
| Property | Primitive Data Types | Non-Primitive Data Types |
|---|---|---|
| Definition | Pre-defined by Java, representing simple, fixed-size data values like numbers or characters. | User-defined or pre-defined types representing more complex structures like arrays, classes, interfaces, etc. |
| Origin | Built into the Java language by the Java compiler. | Defined by the programmer or Java's standard libraries. |
| Examples | Total 8 types i.e. boolean, char, byte, short, int, long, float and double | String, Array, Class, Interface, ArrayList, HashMap, LinkedList, etc. |
| Naming Convention | Typically start with lowercase letters (e.g., int, char, boolean). | Typically start with uppercase letters (e.g., String, ArrayList). |
| Data Type Size | Fixed size regardless of platform (e.g., int is always 4 bytes). | Size depends on the object or class type. For example, the size of an object depends on its fields and internal state. |
| Default Value | Pre-defined default values based on type (int is 0, char is '\u0000', boolean is false). | Default value for reference types is null. |
| Nullability | Cannot be null; they always hold a valid value (e.g., int cannot be null). | Can be null; a reference variable can be uninitialized or point to no object. |
| Data Representation | Represents only one data type (e.g., int for whole numbers, char for a single character). | Can represent multiple data types, and the objects can hold more than one value, making them more flexible (e.g., ArrayList). |
| Performance | Faster, as there is no overhead for reference handling. Direct access to the value stored in memory. | Slower in comparison, as it involves reference handling and dereferencing to access the actual data. |
| Memory Allocation | Stored directly in stack memory. | Stored as references in the stack, while the actual objects reside in heap memory. |
| Value Storage | Stores the actual value. | Stores a reference to the value, not the value itself. |
| Mutability | Immutable by default (e.g., a char cannot change once assigned). | Can be mutable or immutable depending on the object (e.g., String is immutable, ArrayList is mutable). |
| When Copied | When copied, the values are duplicated; the variables hold separate values. | When copied, both reference variables point to the same object in memory. Changes in one will affect the other. |
| Memory Efficiency | More memory-efficient because they directly hold values and do not require additional memory for references. | Less memory-efficient as objects require extra memory for references and internal state. |
| Garbage Collection | Not subject to garbage collection because they are primitive values stored directly in memory. | Subject to garbage collection. When no references to an object exist, it can be collected by the garbage collector. |
| Use Case | Best for simple, small data storage like numeric values, characters, and booleans. | Used for complex data structures or to represent more abstract entities like collections, objects, or user-defined structures. |
| Methods and Operations | Cannot invoke methods directly on primitive types. | Can invoke methods (e.g., String.length() or ArrayList.add()). |
| Example Use Case | Storing simple values like age (int), price (float), or a single character (char). | Representing entities like lists of students (ArrayList), user details (String), or complex collections (HashMap). |
| Write Once, Run Anywhere | Guarantees the same behavior on all platforms due to their fixed size and simple nature. | Can be platform-dependent, especially when objects are heavily dependent on JVM specifics or use specific libraries. |
| Memory Management | Automatically cleaned up when they go out of scope as they are simple data types. | Objects need to be explicitly dereferenced or managed via garbage collection once they are no longer in use. |
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