Defining Classes I - Absolute Java - page 248

• Encapsulation means that the data and the actions are combined into a single item (in
our case, a class object) and that the details of the implementation are hidden . Making
all instance variables private is part of the encapsulation process.
• A class can have two (or more) different definitions for the same method name, pro-
vided the two definitions have different numbers of parameters or some parameters
of differing types. This is called overloading the method name.
• A constructor is a variety of method that is called when you create an object of the
class using new . A constructor is intended to be used to perform initialization tasks
such as initializing instance variables. A constructor must have the same name as the
class to which it belongs.
• A constructor with no parameters is called a no-argument constructor . If your class
definition includes no constructor definitions at all, then Java automatically provides
a no-argument constructor. If your class definition contains any constructor defini-
tions at all, then no additional constructors are provided by Java. Your class defini-
tions should usually include a no-argument constructor.
Answers to Self-Test Exercises
1 . public void makeItNewYears( )
{
month = "January";
day = 1;
}
2 . public void yellIfNewYear( )
{
if ( (month.equalsIgnorewCase("January")) && (day == 1) )
System.out.println("Hurrah!");
else
System.out.println("Not New Year's Day.");
}
3 . public int getNextYear( )
{
int nextYear = year + 1;
return nextYear;
}
4 . public void happyGreeting( )
{
int count;
for (count = 1; count <= day; count++)
System.out.println("Happy Days!");
}