www.pudn.com > SRS.rar > CourseCatalog.java

// CourseCatalog.java - Chapter 16 version. 
 
// Copyright 2000 by Jacquie Barker - all rights reserved. 
 
// An IMPLEMENTATION class. 
 
 
import java.util.*; 
import java.io.*; 
 
public class CourseCatalog extends CollectionWrapper { 
	//------------ 
	// Attributes. 
	//------------ 
 
	// This Hashtable stores Course object references, using 
	// the (String) course no. of the Course as the key. 
 
	private Hashtable courses; 
 
	//---------------- 
	// Constructor(s). 
	//---------------- 
 
	public CourseCatalog() { 
		// Instantiate a new Hashtable. 
 
		courses = new Hashtable(); 
	} 
 
	//----------------- 
	// Get/set methods. 
	//----------------- 
 
 
	//----------------------------- 
	// Miscellaneous other methods. 
	//----------------------------- 
 
	// Used for testing purposes. 
	 
	public void display() { 
		System.out.println("Course Catalog:"); 
		System.out.println(""); 
 
		// Step through the Hashtable and display all entries. 
 
		Enumeration e = courses.elements(); 
 
		while (e.hasMoreElements()) { 
			Course c = (Course) e.nextElement(); 
			c.display(); 
			System.out.println(""); 
		} 
	} 
 
	public void addCourse(Course c) { 
		// We use the course no. as the key. 
 
		String key = c.getCourseNo(); 
		courses.put(key, c); 
	} 
 
	public void parseData(String line) { 
		// We're going to parse tab-delimited records into 
		// three attributes -- courseNo, courseName, and credits -- 
		// and then call the Course constructor to fabricate a new 
		// course. 
 
		// First, make a copy of the record. 
 
		String restOfLine = line; 
 
		// Use the indexOf() method to search for the first 
		// occurrence of a tab character.  The variable "index" 
		// will contain an integer pointing to the character 
		// position in the record (starting with 0 for the first 
		// position) of where the first tab character sits. 
 
		int index = restOfLine.indexOf("\t"); 
 
		// We subdivide the line into two segments:  the portion 
		// which precedes the tab ... 
 
		String courseNo = restOfLine.substring(0, index); 
 
		// ... and the portion which follows it (note that by 
		// adding 1 to the value of index we have jumped past 
		// the first tab character). 
 
		restOfLine = restOfLine.substring(index+1); 
 
		// We now search the REST of the line for the NEXT 
		// tab character, and once again subdivide the 
		// remainder of the record into two segments. 
 
		index = restOfLine.indexOf("\t"); 
		String courseName = restOfLine.substring(0, index); 
		String creditValue = restOfLine.substring(index+1); 
 
		// We have to convert the last value into a number, 
		// using a static method on the Double class to do so. 
 
		double credits = Double.parseDouble(creditValue); 
 
		// Finally, we call the Course constructor to create 
		// an appropriate Course object, and store it in our 
		// collection. 
 
		Course c = new Course(courseNo, courseName, credits); 
		addCourse(c); 
	} 
 
	public Course findCourse(String courseNo) { 
		return (Course) courses.get(courseNo); 
	} 
 
	// We must read a second file defining the prerequisites, in 
	// order to "hook" Course objects together. 
	// This next version is used when reading in prerequisites. 
 
	public void parseData2(String line) { 
		// We're going to parse tab-delimited records into 
		// two values, representing the courseNo "A" of  
		// a course that serves as a prerequisite for  
		// courseNo "B". 
 
		// First, make a copy of the record. 
 
		String restOfLine = line; 
		int index = restOfLine.indexOf("\t"); 
		String courseNoA = restOfLine.substring(0, index); 
		String courseNoB = restOfLine.substring(index+1); 
 
		// Look these two courses up in the CourseCatalog. 
 
		Course a = findCourse(courseNoA);  
		Course b = findCourse(courseNoB);  
		if (a != null && b != null) b.addPrerequisite(a); 
	} 
 
	// Test scaffold. 
	public static void main(String[] args) { 
		// We instantiate a CourseCatalog object ... 
 
		CourseCatalog cc = new CourseCatalog(); 
 
		// ... cause it to read both the CourseCatalog.dat and 
		// Prerequisites.dat files, thereby testing both 
		// the parseData() and parseData2() methods internally 
		// to the initializeObjects() method ... 
 
		cc.initializeObjects("CourseCatalog.dat", true); 
		cc.initializeObjects("Prerequisites.dat", false); 
 
		// ... and use its display() method to demonstrate the 
		// results! 
 
		cc.display(); 
	} 
}