#37 Static Variable in Java

Summary

This video explains the `static` keyword in programming using a mobile phone example. It differentiates between instance variables, which are unique to each object, and static variables, which are shared across all instances of a class. The narrator illustrates how changing a static variable affects all objects, emphasizing best practices for accessing static variables through the class name. By understanding the static keyword, viewers learn about memory efficiency and the importance of class-level variables. The video concludes with a teaser for the next topic: static methods and their relationship with instance variables.

Takeaways

• 😀 The `static` keyword is used to declare class-level variables that are shared among all instances of a class.
• 📱 In a mobile phone class example, instance variables like `brand` and `price` can differ between objects, while a static variable like `name` remains the same across all objects.
• 🔍 Instance variables hold unique values for each object, whereas static variables have a single shared value for all instances.
• 🔗 Changing a static variable through one object affects all other objects of the class since they reference the same static variable.
• ⚙️ Static variables should be accessed using the class name to avoid warnings and adhere to best practices.
• 💡 Using static variables improves memory efficiency by preventing the creation of duplicate copies for each object.
• 🔄 The example illustrates that when the static variable `name` is modified, it updates for all instances of the mobile phone class.
• 🛠️ Instance variables are created in the heap memory, while static variables are stored in a different area in the JVM.
• 📊 It's crucial to understand the distinction between static and instance variables for better code organization and efficiency.
• 🚀 The next video will cover static methods and their relationship with instance variables, expanding the understanding of the static keyword.

Q & A

What does the static keyword in Java signify?

The static keyword indicates that a variable or method belongs to the class itself rather than to any specific instance of the class.

In the provided example, what instance variables are defined in the Mobile class?

The Mobile class has three instance variables: brand (String), price (int), and name (String).

How do static variables differ from instance variables?

Static variables are shared among all instances of a class, meaning they hold a single value for all objects, whereas instance variables have unique values for each object.

What is the effect of making the 'name' variable static in the Mobile class?

Making 'name' static means that it will be common across all Mobile objects; changing it through one object will reflect in all other instances.

Why should static variables be accessed using the class name?

Static variables should be accessed using the class name to avoid confusion and adhere to best practices, as it clarifies that the variable is a class-level variable.

Can you call static variables using instance references?

Yes, you can call static variables using instance references, but it is discouraged and can lead to compiler warnings.

What happens in memory when multiple objects of the Mobile class are created?

Each object has its own instance variables stored separately in memory, while static variables are stored in a shared area and are not duplicated for each instance.

How can you change the value of a static variable?

You can change the value of a static variable using the class name followed by the variable name, e.g., Mobile.name = 'New Value'; this change will affect all instances of the class.

What are the advantages of using static variables?

Static variables help save memory by sharing a single variable among all instances, and they provide a way to maintain common data across objects.

What will be discussed in the next video related to static variables?

The next video will cover static methods and explore whether instance variables can be used within static methods.