Java iq #14 - Difference between Primitive & Reference datatypes #javainterviewquestions

In Java, data types can be broadly categorized into two groups: primitive data types and reference data types. Understanding the difference between these two is crucial for effective Java programming. Here are the key differences:

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Primitive Data Types
Definition: Primitive data types are the most basic data types available in Java. They are predefined by the language and named by a reserved keyword.

Types: Java has eight primitive data types:

byte
short
int
long
float
double
char
boolean
Memory Allocation: Primitive data types are stored directly in the stack. The size of the memory allocated for each primitive type is fixed and depends on the type itself (e.g., int is 4 bytes, double is 8 bytes).

Value Storage: They store actual values. For example, an int variable might store the number 42.

Default Values: Primitive data types have default values if not explicitly initialized:

byte, short, int, long default to 0
float, double default to 0.0
char default to '\u0000' (null character)
boolean default to false
Operations: They can be used with arithmetic and logical operations directly.

Reference Data Types
Definition: Reference data types are used to refer to objects. They are created using constructors of classes.

Types: Reference types include:

Classes (e.g., String, Scanner, user-defined classes)
Arrays
Interfaces
Memory Allocation: Reference data types are stored in the heap memory. The reference (or address) to the actual object is stored in the stack.

Value Storage: They store references (memory addresses) to the actual objects, not the objects themselves. For example, a String variable might store the reference to the location of the string value.

Default Values: Reference types default to null if not explicitly initialized.

Operations: Operations on reference types usually involve method calls, and they cannot be used directly in arithmetic operations. Instead, you need to use methods defined in the classes.