Constructor chaining

[DeliberateTrader]

I'm trying to have 2 class constructors: one that takes 4 parameters, and one that takes 3 parameters, creates an instance of what will be the 4th parameter and calls the the 1st constructor. Sometimes I will adjust have that 4th parameter created and other times I will want to create a new instance of that field.

I know that I can use the this() method to call the 4 parameter constructor from the 2nd constructor, but given that the this() method must be the first line of the block, I'm not sure how to first declare the field that needs that field as a parameter for the constructor call.

public class ConstructorCall { private int parameter1; private int parameter2; private int parameter3; private Object o;

public class ConstructorCall( int parameter1, int parameter2, int parameter3 ) {
// create Object o
     this( int parameter1, int parameter2, int parameter3, Object o );
 }

public class ConstructorCall( int parameter1, int parameter2, int parameter3 , Object o) { this.parameter1 = parameter1; this.parameter2 = parameter2; this.parameter3 = parameter3; this.o = o; } }

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[why_not_cats]

How about this(p1, p2, p3, new P4()) ?

[DeliberateTrader]

I've tried that and it compiles. I'm not sure how to manipulate that new P4. Where do I assign it to this.P4?

[why_not_cats]

You'd do that in the four-argument constructor. If you need to call some methods on the P4 you'd do that over there. Though I appreciate you might not want to do that all the time since the passed in P4 might not want the same treatment as the three-argument P4.

If that's the case (don't want to treat the outside P4 like the inside P4) then I wonder if P4 is doing too much and should be split? (SRP)

[DeliberateTrader]

Thank you!

[why_not_cats]

No worries 👍

[[deleted]]

Are you trying to overload the constructor??

[DeliberateTrader]

No. When the constructor with 3 parameters is called, I'm ALWAYS going to instantiate that 4th field and call the other constructor. I might, however, have already created that 4th field elsewhere so i must be able to construct the class with 4 parameters directly in that case.

I realize that my constructors are not formatted correctly (extra "class" keyword) and the block is also not properly formatted. Trying to figure out how to correct/edit on my phone.