What keyword is used in Java to define a constant?

The keyword used in Java to define a constant is "final." When a variable is declared as final, it means that once it has been initialized with a value, that value cannot be changed throughout the program. This is particularly useful for defining constants, which are values that should remain constant and should not be modified.

For instance, if you declare a constant for the value of pi, you would do so by using the final keyword like this:

final double PI = 3.14159;

Here, PI is a constant because it is declared with the final keyword, ensuring that its value cannot be altered later in the code.

The other terms provided do not serve the same purpose in Java. "Static," for example, is used to indicate that a variable or method belongs to the class rather than instances of the class, which is unrelated to defining constants. "Const" is a keyword found in some other programming languages but not in Java, while "immutable" is a concept that refers to objects that cannot be changed after they have been created, but it is not a keyword used to declare constants. Thus, final is the correct and direct keyword to utilize when defining constants in Java.