Static Variables in Java – A Complete Overview with Examples

Java has three kinds of variables: instance, local, and static. The instance variables belong to the individual objects, while the static ones are attached to the class. All the class objects will share a static variable and contain one single copy, no matter how many instances you may create. Let’s explore static variables in Java in detail!

What is a Static Variable in Java?

A Java static variable is shared among all the class instances. Whereas instance variables are unique to every object, a static variable does not belong to any particular instance but rather to the class itself. Changes made to a static variable by any instance are reflected across all class instances. Static variables store data that should be common to all class objects rather than unique to each instance.

Java Developer also used a static variable as a constant with the final keyword. Constants must be initialized during the declaration. It means the declaration cannot be changed after being assigned.

The following program demonstrates the Initialization of static final variables in Java language.

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Properties of Static Variables

Static variables in Java have several distinct properties that differentiate them from instance variables. Here are the key properties.

• Class-Level Scope: Static variables are associated with the class rather than any particular instance. This means that they are shared across all instances of the class.

• Single Copy: There is only one copy of a static variable, regardless of the number of objects created from the class. All objects share the same copy of the static variable.

• Memory Allocation: Static variables are allocated memory only once when the class is loaded into memory by the Java ClassLoader. They are stored in the method area of the memory, also known as the ‘class area.’

• Default Values: Static variables are initialized to their default values if not explicitly initialized. A static int variable will be initialized to ‘0’, a static boolean will be ‘false,’ and so on.

• Scope: The scope of static variables is very limited to the class in which it is declared. Its visibility to others depends on its access modifiers (e.g., ‘public’ and ‘protected’).

• Inheritance: Static variables are inherited by a subclass, but each subclass shares the same copy of the static variable as the parent class.

• Access: Static variables can be accessed using the className. We can also access the static variable using a class instance.

Storage Area of Static Variable in Java

The static variable and method are stored in the heap memory. It is a specific part of the heap memory dedicated to storing class-level information. When a class is loaded by the JVM, its static variables are allocated memory in this method area, which is shared across all class instances. This ensures that static variables are initialized once and accessed directly through the class name rather than individual object instances.

How to Declare a Static Variable in Java?

We can declare a static variable through the use of a static keyword. Static variables belong to the class rather than to any specific class instance. This means that all instances of the class share the same static variable.

Declaration of Static Variables

The following program demonstrates the static variable in Java.

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Accessibility of the Static Variable in Java

In Java, a static variable is associated with a class rather than a class instance. There is no need to create an object to access the static variables because static variables are the class variables, and static variables are shared among all the class instances. Simply, we can access the static variable using the class name. (eg, ‘ClassName.variableName’).

• ClassName: The name of the class that contains the static variable.
• Dot Operator: Operator used to access static variables.
• VariableName: The name of the static variable that needs to be called in a Java program.

The following program demonstrates the accessibility of static variables.

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What is the Use of Static Keywords in Java?

The ‘static’ keyword in Java is primarily used for memory management and to define class-level elements.

• Class-Level Variables: Static variables are also known as class variables because they belong to the class rather than any specific class instance. This means that all instances of the class share the same static variable.

• Memory Efficiency: Static variables are shared across all instances. Memory allocation for these variables happens only once, making the program more memory-efficient.

Syntax of Static Variable in Java

static datatype variableName = Value;

The following program demonstrates the static variable in Java.

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Real-world Example of Static Variable in Java

An example of a static variable in real life is the use of a static counter in Java to define how many times an object was instantiated from a class. The situation occurs whenever the course of the execution of a program is to be observed in terms of the number of instances of a given class.

The following program demonstrates a real-life example in Java.

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Conclusion

Static variables in Java are an essential aspect of class-level data management. They can save on memory, as they are shared across all instances of the class, but allow easy access to common values. Thus, a Java programmer should understand how to declare, initialize, and use static variables. With their ability to maintain a single copy of a variable for all objects, static variables help in scenarios where a standard resource or configuration is needed. This concept is fundamental for any Java developer looking to write clean and optimized source code.