'Blank' final fields : final « Class Definition « Java Tutorial

1. Java Tutorial
2. Class Definition
3. final

class A {
  private int i;

  A(int ii) {
    i = ii;
  }
}

public class MainClass {
  private final int i = 0; // Initialized final

  private final int j; // Blank final

  private final A a; // Blank final reference

  // Blank finals MUST be initialized in the constructor:
  public MainClass() {
    j = 1; // Initialize blank final
    a = new A(1); // Initialize blank final reference
  }

  public MainClass(int x) {
    j = x; // Initialize blank final
    a = new A(x); // Initialize blank final reference
  }

  public static void main(String[] args) {
    new MainClass();
    new MainClass(47);
  }
}