Java: An Object Constructor Passing Same Object as Parameter

Question

I have made an object called Transaction which I am passing in an ArrayQueue.

Here is the Transaction class constructors (I have the appropriate setter and getters too):

public class Transaction {

    private int shares;
    private int price;

    public Transaction(int shares, int price) {
       this.shares = shares;
       this.price = price;
    }

    public Transaction(Object obj) {
       shares = obj.getShares();
       price = obj.getPrice();
    }
}

In the second constructor there I am wanting a scenario where I can pass into it a different Transaction object that has been dequeue(ed) and get the info from that transaction and make it into a new transaction or possibly manipulate it before I put it back into the queue. But when I compile it does not like this.

Is this acceptable programming practice to pass a specific object into it's own object's constructor? Or is this even possible?

Answer 1

It's called copy-constructor and you should use public Transaction(Transaction obj) instead of Object and also provide getters:

public class Transaction {

    private int shares;
    private int price;

    public Transaction(int shares, int price) {
       this.shares = shares;
       this.price = price;
    }

    public Transaction(Transaction obj) {
       this(obj.getShares(), obj.getPrice()); // Call the constructor above with values from given Transaction
    }

    public int getShares(){
        return shares;
    }

    public int getPrice(){
        return price;
    }
}

Answer 2

You need to specify the same type:

public Transaction(Transaction obj) {
       shares = obj.getShares();
       price = obj.getPrice();
    }

Provided that you have defined getShares() and getPrice().