Ernest Friedman-Hill wrote:Defining a "default" (you mean no-argument) constructor in every class is not a good practice. Never define methods or constructors you don't imagine being used.
Adding "super()" explicitly as the first line of every constructor is likewise not a good practice; it's extra code, for no reason. Don't clutter your code with things you don't need.
Finally, explicitly initializing instance variables to null, and then later setting them to their actual values, is again not a good practice. Initialize them at the point where you have all the information needed to set their initial values, and no earlier.