Discovering Classes and Objects - Beginning Java 7 - page 85

int balance;
SavingsAccount deposit(int amount)
{
balance += amount;
return this;
}
SavingsAccount printBalance()
{
System.out.println(balance);
return this;
}
public static void main(String[] args)
{
new SavingsAccount().deposit(1000).printBalance();
}
}
Listing2-10 showsthatyoumustspecifytheclass'snameastheinstancemethod'sre-
turntype.Eachof deposit() and printBalance() mustspecify SavingsAc-
count asthereturntype.Also,youmustspecify return this; (returncurrentob-
ject's reference) as the last statement—I discuss the return statement later.
For example, new SavingsAc-
count().deposit(1000).printBalance(); creates a SavingsAccount
object, uses the returned SavingsAccount reference to invoke SavingsAc-
count 's deposit() instancemethod,toaddonethousanddollarstothesavingsac-
count (I'm ignoring cents for convenience), and finally uses deposit() 's returned
SavingsAccount reference(whichisthesame SavingsAccount instance)toin-
voke SavingsAccount 's printBalance() instancemethodtooutputtheaccount
balance.
Declaring and Invoking Class Methods
In many situations, instance methods are all that you need. However, you might en-
counter a situation where you need to describe a behavior that is independent of any
object.
Forexample,supposeyouwouldliketointroducea utility class (aclassconsistingof
static [class] methods) whose methods perform various kinds of conversions (such