declaration: this is called a "blank final" variable. A blank final instance variable of a class must be definitely assigned in every constructor of the class in which it is declared; similarly, a blank final static variable must be definitely assigned in a static initializer of the class in which it is declared; otherwise, a compile-time error occurs in both cases. (Note: If the variable is a reference, this means that the variable cannot be re-bound to reference another object. But the object that it references is still mutable, if it was originally mutable.) Unlike the value of a constant, the value of a final variable is not necessarily known at compile time. It is considered good practice to represent final constants in all uppercase, using underscore to separate words. Example: public class Sphere { // pi is a universal constant, about as constant as anything can be. public static final double PI = 3.141592653589793; public final double radius; public final double xPos; public final double yPos; public final double zPos; Sphere(double x, double y, double z, double r) { radius = r; xPos = x; yPos = y; zPos = z; } [...] } Any attempt to reassign radius, xPos, yPos, or zPos will result in a compile error. In fact, even if the constructor doesn't set a final variable, attempting to set it outside the constructor will result in a compilation error. To illustrate that finality doesn't guarantee immutability: suppose we replace the three position variables with a single one: public final Position pos; where pos is an object with three properties pos.x, pos.y and pos.z. Then pos cannot be assigned to, but the three properties can, unless they are final themselves. Like full immutability, the use of final variables has great advantages, especially in optimization. For instance, Sphere will probably have a function returning its volume; knowing that its radius is constant allows us to memoize the computed volume. If we have relatively few Spheres and we need their volumes very often, the performance gain might be substantial. Making the radius of a Sphere final informs developers and compilers that this sort of optimization is possible in all code that uses Spheres. Though it appears to violate the final principle, the following is a legal statement: for (final SomeObject obj : someList) { // do something with obj } Since the obj variable goes out of scope