ISE 582: Web Technology for
Industrial Engineering
University of Southern California
DJE Dept of Industrial and Systems Engineering
Lecture 7
JAVA Cup 7: It’s all in the Packaging
Handouts
• Lecture 7 slides
• READ Winston & Narasimhan :
– Chapters 33-38 (pp 201-233)
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JAVA Cup 7
• Characters and Strings
– Codestrings and delimiters
• How to Read/Write Objects
• How to Modularize Programs
• Creating a Window
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Specifying Delimiters
• You can use codestrings to specify interesting
information in textfile
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Specifying Delimiters
• To advise the tokens tokenizer to use
double quotation marks to delimit
strings:
– tokens.quoteChar((int) ‘”’)
• To tell the tokenizer to recognize
carriage returns:
– tokens.eolIsSignificant(true);
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Working with O/p File Streams
• To connect to output file
– FileOutputStream stream = new
FileOutputStream(“output.data”);
• To write more than 1-byte-at-a-time
– PrintWriter writer = new PrintWriter(stream);
• It’s good to flush out buffered characters
– writer.flush()
• Close the file
– stream.close()
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Reading / Writing Objects
• Serialized input-output operations
– <obj.o/p.stream>.writeObject(<vector>)
– <obj.i/p.stream>.readObject()
• Indicate intentions to use operations by
– implements Serializable
– throws IOException, ClassNotFoundException
• Each instance must belong a class that implements the
Serializable Interface
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Review
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stream
reader
buffer
stream
reader
tokens
stream
writer
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Reading Objects from File
FileInputStream fileInputStream
= new FileInputStream(“in.data”);
ObjectInputStream objectInputStream
= new ObjectInputStream(fileInputStream);
Vector <vector>
= (Vector) objectInputStream.readObject();
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To Write Objects to File
FileOutputStream fileOutputStream = new
FileOutputStream(“out.data”);
ObjectOutputStream objectOutputStream = new
ObjectOutputStream(fileOutputStream);
objectOutputStream.writeObject(<vector>);
objectOutputStream.close();
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Modularing Your Program
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•
•
•
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Compilation Units
Packages
Setting CLASSPATH
Calling Methods from a Module
Access to Var/Methods in Package
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Compilation Units
• Define all classes in same file
• Only one class can be public
• Only one class is universally
accessible
• Convention: each class has its own
compilation unit
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Packages
• Use single-class compilation units
• Indicate module using package
statement at beginning of each c.u
– package onto.java.entertainment;
• Convention: package names consist of
components separated by dots
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CLASSPATH
• Package names correspond to paths
– package onto.java.entertainment;
– Files stores in ./onto/java
• Setting the path
UNIX
– setenv CLASSPATH <path1>:<path2>:.
– setenv CLASSPATH=<path1>;<path2>;.
PC
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Using Methods from a Package
• First import package
– import onto.java.entertainment.*
– Auxiliaries.readMovieFile(“input.data”)
– ((Movie) vectorElement).rating()
• Or, refer to entire name
– onto.java.entertainment.Auxiliaries.readMovieFile
(“input.data”)
– ((onto.java.entertainment.Movie)
vectorElement).rating()
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Access to Variables/Methods
• private :
– available only to methods inside own class
• protected :
– available to methods in same class, c.u. or package, subclasses
• No keyword :
– available only to c.u. or package
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How to Create Windows
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•
•
•
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Nomenclature
Intro to Swing classes
Hierarchy of Swing classes
Listener Classes
Window Creation Pattern
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Nomenclature
• GUI (pronounced goo-ey) :
– Graphical User Interface
• Components :
– class instances that have a graphical representation
• Containers :
– components that allow nesting of other containers inside
their boundaries
• Window :
– a container’s graphical representation
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Introduction to Swing (J) Classes
• API = Application Programmer’s Interface
• The AWT Package: java.awt.*
– AWT = Abstract Window Toolkit
– contains Component, Container classes
• The Swing Package: java.swing.*
– contains JFrame, JApplet, JComponent, JPanel classes
• Try to restrict display work to Swing classes
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Hierarchy of Swing Classes
Component
Container
Window
Panel
Frame
Applet
JFrame
JComponent
JPanel
JList
JLabel
JTextField
JApplet
JButton
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Example: A Window
import javax.swing.*;
public class Demonstrate {
public static void main (String argv []) {
JFrame frame = new JFrame (“I am a
window, square and proud”);
frame.setSize(200,200);
frame.show();
}
}
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Listener Classes
• Event as a state change
– Mouse clicks and key presses
– Variable-value changes
• Event as instance of EventObject class
– Describes state change
• Java deals with events through Listener Classes
• Listener classes are defined by
– Extending existing listener classes
– Implementing listener interfaces
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Example: Link listener to frame
• When mouse clicks:
– a WindowEvent instance is created
– the windowClosing method is called with
connected listener as target and
WindowEvent instance as arg
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Adapter Classes
• Adapter classes implement all
interface-required methods as donothing methods.
• You can define shadowing methods in
your subclass for whatever subset of
methods you need
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Nesting Class Definitions
• Advantage of nesting classes:
– Method definition (windowClosing)
appears in proximity to window definition
– Can reuse names of private classes such
as LocalWindowListener
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Window Creation Pattern
• Define a subclass of JFrame class
• Main method calls constructor
• Constructor:
– assigns title, size, and displays a window
– creates required class instances
– connects class instances
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