In Java, final is an access modifier. It could be used to modify:
final for class
class: this means the class cannot be inherited by subclasses.
public final class Dog extends Animal
{
// code
}
final for method
method: this means the method cannot be overwritten by subclasses. Use this if you want this method to be non-modifiable by subclasses.
public class Aminal
{
// other code
public final eat() {
// code
}
}
final for variable
variable: this means the variable can only be assigned once. Use this when you want a constant variable. Typical usage is like
final double PI = 3.14159;
Also, we remark that Math.PI is a built-in constant variable declared using final. Math is a build-in final class that cannot be inherited.
A peek to the Math class:
public final class Math {
/**
* Don't let anyone instantiate this class.
*/
private Math() {}
/**
* The {@code double} value that is closer than any other to
* <i>e</i>, the base of the natural logarithms.
*/
public static final double E = 2.7182818284590452354;
/**
* The {@code double} value that is closer than any other to
* <i>pi</i>, the ratio of the circumference of a circle to its
* diameter.
*/
public static final double PI = 3.14159265358979323846;
// ... other code ...
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