Question

I have an abstract class called account which is as follows –

abstract class Account
{
    private int number;
    private String owner;

    public Account(int accountNumber, String  accountOwner)
    {
        number = accountNumber;
        owner = accountOwner;
    }

    public int getAccountNumber(){ return number; }
    public String getAccountOwner(){ return owner; }
    public abstract double getBalance();
    public abstract double  makeDeposit(double  amount);
    public abstract double  makeWithdrawal(double  amount);
}

This class defines the basic skeleton for an account. Several specialized account class will be created by inheriting this class, such as MarketSavingsAccount, RegularSavingsAccount etc.

Now I have an array which is declared as follows –

Account[] accounts

which contains a list of accounts. In this array different types of accounts are available. Now how can I determine which of these array members is an instance of MarketSavingsAccount?

Answer 1

From a pure OOP standpoint you’re not supposed to care; you’re supposed to avoid downcasting and treat all the Account instances the same.

But enough theory – you’re probably looking for instanceof, as in

Account a = accounts[0];
if (a instanceof MarketSavingsAccount)
{
    ...
}