Final keyword is used in severl different contexts as a modifier meaning that what it modifies cannot be changed in any sense.
Final classes:
For example,
class Sample
{
----
----
}
This means that this class will not be subclassed.It provides benfit for security and thread safety.
String class is defined final to prevent creating a subclass. If you try to access the class(which is declared as final class) , then you will get a compiler error.
Final Method:
You can use the final keyword in a method declaration to indicate that the method cannot be overridden by subclasses.
For example, the object class has some methods as final and some are not.
Final Fields:
When a field is declared final, it is treated as a constant. and cannot be changed.
If you try to change the value,then, compile time error or an exception is generated.
For example:
class Myclass
{
final int n=10;
}
class My
{
public static void main(String args[])
{
Myclass m = new Myclass();
System.out.println("Constant value is "+m.n);
}
}