Transcript Chapter 2: Loops and Logic

Chapter 5: Defining Classes
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Basics of Classes
• An object is a member of a class type
• What is a class? Fields & Methods
• Types of variables:
– Instance: each instance (object) of the class will have its own
copy of instance variables
– Class: Only one copy is shared by all objects
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Types of methods: Instance & class (static) method
Accessing variables and methods (dot operator)
Accessing static variables and methods?
Methods: name, return value, & parameters
Acessing class Data members in methods
Example: p. 181 Sphere.java
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Basics of Classes (cont)
• Initialization blocks are used to initialize large
number of variables like the element of a large
array. Page 184 (try non static)
• Constructor: Mainly for guaranteeing that class
variables are properly initialized. P. 186: Sphere
& CreateSphere (Compile & run)
• Method overloading and multiple constructors
(195-Sphere)
• Using objects (197-Point, 199-Line, & 201TryGeometry)
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JAVA Packages
• Recursion means a method can call itself!! A behavior
that can be very useful. Ex: 203-PowerCalc.java
• A Java package is basically a group of Java classes
stored in a directory that has the exact name as the
package name
• To create a package use the “package <name>” as the
first statement in all the classes of that package
• To compile a class in a package, the path to that
package should be defined in your “classpath” var.
• To run a class in a package, you need to run JVM from
the upper directory containing that package and to
specify the name of the package & the class name
separates by a period.
• Standard Java packages. See documentation
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Access Attributes & Nested Classes
• There are four attributes: friendly, public,
private, and protected
• Ex: 217-Point, 218-Line, & 219-TryPackage
• Java nested classes & static nested classes.
Ex: 224-MagicHat & 225-TryNesstedClasses
• Using Non-static nested classes. Ex: 227MagicHat
• The finalize() method
• You can declare native methods using the
“native” keyword but you lose portability.
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