Question

class X
{
  String x1;
  String x2;
  //...
  String x15;

  public X (Other o)
  {
    // initialize x1,x2,...,x15
  }

  String getx1 () { return x1; }  // lot of getters
  String getx2 () { return x2; }
  //...
  String getx15 () { return x15; }
}

The object of class X is initialized in constructor of class Other;

class Other
{
  private X obj;
  // Other members
  public Other ()
  {
    obj = new X(this);
    //...
  }
  //...
}

I want to somehow get rid of lot of getter methods in class X. I can simply remove those and make all the data members of X in default scope (X is used only within package).

Is there any way by which I can make the members of X obj un-mutable after the constructor Other is called ? Here the idea is, when using get() methods, the variables inside X cannot be modified.

obj.getx1();

Now, if I use simply obj.x1 then there are chances that it might get overwritten (or at least in code review, it will be objected).

[Note: obj has to be initialized in the Other() constructor only].

Answer 1

Best way to make a class immutable (not un-mutable) is to mark all fields as final (visibility is irrelevant, can be public). Fields must be initialized either with an initializer:

class A { final int x = 10; }

or in every constructor:

class A { 
   final int x, y, z;
   A(int x, int y, int z) { this.x = x;, this.y = y; this.z = z; }
   A() { this (0, 0, 0); }
}