What is the use of static variables?

A static variable in Java is:

A class-level variable shared by all instances of that class.

It’s declared using the static keyword inside a class but outside any method or constructor.

🔍 Syntax Example

public class Employee {
    static int count = 0;  // Shared by all Employee objects

    public Employee() {
        count++;  // Increment every time a new Employee is created
    }
}

In this example, no matter how many Employee objects are created, count belongs to the class, not to any single object.

🎯 Why Use Static Variables?

🧪 Real-World Example

public class BankAccount {
    static String bankName = "SafeTrust Bank";

    int accountNumber;
    double balance;

    // All accounts share the same bank name
}

All accounts created from BankAccount share the same bankName. You can change it globally with:

BankAccount.bankName = "NewSecure Bank";

🧠 Key Characteristics

• Belongs to the class, not object
• Loaded once when the class is loaded into memory
• Shared across all instances
• Can be accessed as ClassName.variableName
• Often used with static methods

🚨 Common Mistakes (And Interview Gotchas)

✅ Final Interview Takeaways

• Use static when the variable’s value should be shared globally across all objects.
• Think of it as a single copy sitting in memory, no matter how many objects you create.
• It’s excellent for counters, constants, configuration values, or utility class state.
• Pair it with static blocks or static methods for consistent utility or logic encapsulation.