Types of Variables in Java with Examples
In Java, variables are classified into different types based
on their scope, lifetime, and how they are stored. The main types of variables
in Java are:
1. Local Variables
- Declared
inside a method, constructor, or block.
- Can
only be used within that method or block.
- Must
be initialized before use.
- Stored
in the stack memory.
Example:
java
public void
display() {
int x = 10; // Local variable
System.out.println(x);
}
2. Instance Variables (Non-Static Variables)
- Declared
inside a class but outside any method.
- Each
object of the class gets its own copy.
- Stored
in the heap memory.
- Default
values are assigned (e.g., 0 for integers, null for objects).
Example:
java
class Person
{
String name; // Instance variable
}
3. Static Variables (Class Variables)
- Declared
using the static keyword inside a class but outside methods.
- Shared
among all instances of the class.
- Stored
in the method area (static memory).
- Default
values are assigned automatically.
Example:
java
class Employee
{
static String company = "TechCorp";
// Static variable
}
4. Final Variables (Constants)
- Declared
using the final keyword.
- Once
assigned, their value cannot be changed.
- Can
be local, instance, or static.
Example:
java
final int
MAX_VALUE = 100; // Final variable
5. Volatile Variables
- Declared
using the volatile keyword.
- Used
in multithreading to ensure visibility of changes to variables across
threads.
Example:
java
class SharedData
{
volatile int counter = 0; //
Volatile variable
}
6. Transient Variables
- Used
in serialization to exclude a variable from being serialized.
- Declared
using the transient keyword.
Example:
java
class User
implements Serializable {
transient String password; //
Transient variable
}
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