Final Field

A final field can only be initialized once and cannot be modified afterward (similar to const in C++).

Types of final fields:

1. Static Final Fields: Initialized when declared.

   static final double PI = 3.14159;

2. Instance Final Fields: Initialized in the constructor.

   public class Person {
       String name;
       final String eyeColor;
       final String socialSecurityNumber;
   
       public Person(String name, String eyeColor, String socialSecurityNumber) {
           this.name = name;
           this.eyeColor = eyeColor;
           this.socialSecurityNumber = socialSecurityNumber;
       }
   }
   
   Person somePerson = new Person("John Doe", "green", "1234-5678");
   
   // This is allowed
   somePerson.name = "Jack Doe";
   
   // This causes an error because 'eyeColor' is final
   somePerson.eyeColor = "blue";  

Final fields can be initialized during the object's creation, but once set, they cannot be changed.