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It's important to note that static methods and variables cannot access non-static methods or variables, because they are not associated with any particular class instance.
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Static Variable
To declare a static variable, you put them in the class just like instance variables, but you put the keyword static in front. Static variables belong to the class and have one copy. When a value is stored in a static variable, it is not stored in the object of the class. Static variables are useful to keep information that is common to every object.
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A common example of using static members in a Java class is for utility methods and constants that should be shared across all instances of the class. For instance, let's consider the case of a MathUtility class that contains various mathematical utility methods and constants.
Example 1: Constants
You might have mathematical constants like Pi (π) and Euler's number (e) that don't change and should be the same for all instances. Making them static ensures there's only one copy for all objects, which is memory-efficient.
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double circleArea = MathUtility.PI * radius * radius; |
Example 2: Utility Methods
Let's say you often need to calculate the factorial of numbers. Rather than writing this code everywhere you need it, you can encapsulate it in a static method inside a utility class.
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long result = MathUtility.factorial(5); // Output will be 120 |
Example 3: Counting Instances
Static members can also be used for counting the number of instances of a class that have been created, which can be useful for debugging or monitoring resource usage.
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In summary, static members are useful when you need to share common data or behavior across all instances of a class, rather than replicating that data for each individual instance.
Static Methods
A static method can be accessed by using the name of the class. So you don't need to create an instance to access the method. Methods can also be declared static by placing the static keyword between the access modifier and the method's return type. When a class contains a static method, it is not necessary to create an instance of the class to use the method.
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