Is it better to assign variables in a class itself or in the class' constructor? [closed]

Question

This is a sort of design question, and I'm sure there are people who do it both ways. But in your opinion, is it better to assign a variable in the class or in the constructor? For example (regardless of syntax or language, this is just to explain):

public class Example
{
   private final int TIME_STAMP = Now();
   private int num = 2;
}

OR

public class Example
{
   private readonly int TIME_STAMP;
   private int num;

   public Example()
   {
      TIME_STAMP = Now();
      num = 2;
   }
}

Please disregard the mix of different languages and syntax... Which is preferable and why?

Answer 1

In tend to :

• Set default, constant values in the class itself
• And values that depends on something else (like the current time) in the constructor.

i.e., I tend to use something like this (merging your two examples) :

public class Example
{
   private readonly int TIME_STAMP;
   private int num = 2;

   public Example()
   {
      TIME_STAMP = Now();
   }
}

But my prefered language is PHP, and it doesn't allow me to set non-constant values in the class declaration itself, so my way might be a bit biased.

Answer 2

Inline (the first option):

• it is more readable
• you don't have to duplicate it in every constructor

• if there is such thing in your language, you can use initializer blocks. They look like constructors, but don't need to be defined multiple times. In Java they look like this:

  {
      var1 = 5;
      varTime = now();
  }