I am told to declare and initialize my class constant. I didn't know what it was so I searched google, apparently everyone already knows what it is and nobody has asked on it. So what is a class constant? Is it just a value that doesn't change throughout the class?
Class constants can be useful if you need to define some constant data within a class. A class constant is declared inside a class with the const keyword. Class constants are case-sensitive. However, it is recommended to name the constants in all uppercase letters.
Introduction to Python Class Constants. An unchangeable value, assiged, is called a constant. Meaning, constants are the containers that hold some information and cannot be changed further. Write once, read many times constants are created in the class of Python. Usually, constants are defined in the level of a module.
A constant is a variable whose value cannot change once it has been assigned. Java doesn't have built-in support for constants. A constant can make our program more easily read and understood by others. In addition, a constant is cached by the JVM as well as our application, so using a constant can improve performance.
Constant: A constant can be defined as a fixed value, which is used in algebraic expressions and equations. A constant does not change over time and has a fixed value. For example, the size of a shoe or cloth or any apparel will not change at any point.
JLS-8.3.1.1. static
Fields says (in part)
A
static
field, sometimes called a class variable, is incarnated when the class is initialized (§12.4).
JLS-4.12.4. final
Variables says (in part)
A constant variable is a
final
variable of primitive type or typeString
that is initialized with a constant expression (§15.28)
Putting that together, a class constant is a static final
field.
Class variables are static; instance variables are not.
Final variables are constant.
So a class constant would be declared like this:
public class Foo {
// Class constant
public static final String DEFAULT_NAME = "Bar";
public static void main(String [] args) {
String name = Foo.DEFAULT_NAME;
}
}
It's the same for all instances of Foo
.
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