Java Objects
Objects are containers around aggregates of primitive types, arrays, and other
objects
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Properties of Classes
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All Java code is contained within objects
Excepted comments, import and package statements.
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Objects are passed to methods by reference
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Definition, declaration, and creation of objects are distinct
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Instances of objects are created with new and have a value of null
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Objects have four forms: the class, the abstract class, the inner class,
and the interface
class Circle // object definition
{ static double pi = 3.141592; // class variable
double radius; // instance variable
public Circle(double r) // constructor method
{ radius = r;
}
public double circumference() { return 2*pi*radius; }
public double area() { return pi*radius*radius; }
public static getPi() { return pi; } // class method
}
Circle c; // object declaration
c = new Circle(4.0); // object creation
double a = c.area(); // object method call