Variables in Java

Static Variables in Java Static variables in Java are class-level variables that are shared among all instances of the class. Here are the key characteristics: Key Features Class-level storage: Belongs to the class rather than any specific instance Single copy: Only one copy exists regardless of how many objects are created Shared access: All instances share the same static variable Memory allocation: Created when the class is loaded and destroyed when the class is unloaded Declaration Syntax class MyClass { static int count; // static variable // ... } When to Use Static Variables When you need a variable common to all objects of a class For constants (usually combined with final) For maintaining counts or other shared states across instances Important Notes Access: Can be accessed using either: Class name: MyClass.count Instance reference: obj.count (not recommended) Initialization: Default values (0, null, false etc.) if not initialized Can be initialized at declaration or in static blocks Thread Safety: Static variables are not thread-safe by default - need synchronization in multi-threaded environments Example public class Employee { static int employeeCount = 0; // static variable public Employee() { employeeCount++; // increments for each new Employee created } public static void main(String[] args) { new Employee(); new Employee(); System.out.println("Total employees: " + Employee.employeeCount); // Output: 2 } } Static variables are useful for maintaining shared state across all instances of a class, but should be used judiciously to avoid unintended side effects.

Apr 17, 2025 - 19:28

Static Variables in Java

Static variables in Java are class-level variables that are shared among all instances of the class. Here are the key characteristics:

Key Features

Class-level storage: Belongs to the class rather than any specific instance
Single copy: Only one copy exists regardless of how many objects are created
Shared access: All instances share the same static variable
Memory allocation: Created when the class is loaded and destroyed when the class is unloaded

Declaration Syntax

class MyClass {
    static int count;  // static variable
    // ...
}

When to Use Static Variables

When you need a variable common to all objects of a class
For constants (usually combined with final)
For maintaining counts or other shared states across instances

Important Notes

Access: Can be accessed using either:
- Class name: MyClass.count
- Instance reference: obj.count (not recommended)
Initialization:
- Default values (0, null, false etc.) if not initialized
- Can be initialized at declaration or in static blocks
Thread Safety: Static variables are not thread-safe by default - need synchronization in multi-threaded environments

Example

public class Employee {
    static int employeeCount = 0;  // static variable

    public Employee() {
        employeeCount++;  // increments for each new Employee created
    }

    public static void main(String[] args) {
        new Employee();
        new Employee();
        System.out.println("Total employees: " + Employee.employeeCount);  // Output: 2
    }
}

Static variables are useful for maintaining shared state across all instances of a class, but should be used judiciously to avoid unintended side effects.