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chapter09.java
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303 lines (240 loc) · 7.15 KB
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// A short package demonstration.
package bookpack;
class Book {
private String title;
private String author;
private int pubDate;
Book(String t, String a, int d) {
title = t;
author = a;
pubDate = d;
}
void show() {
System.out.println(title);
System.out.println(author);
System.out.println(pubDate);
}
}
class BookDemo {
public static void main(String[] args) {
Book[] books = new Book[5];
books[0] = new Book("The Art of Computer Programming, Vol 3",
"Knuth", 1973);
books[1] = new Book("Moby Dick",
"Melville", 1851);
books[2] = new Book("Thirteen at Dinner",
"Christie", 1933);
books[3] = new Book("Red Storm Rising",
"Clancy", 1986);
books[4] = new Book("On the Road",
"Kerouac", 1955);
for(int i=0; i < books.length; i++) {
books[i].show();
System.out.println();
}
}
}
// -----------------------------------------
// Book recoded for public access.
package bookpack;
public class Book {
private String title;
private String author;
private int pubDate;
// Now public.
public Book(String t, String a, int d) {
title = t;
author = a;
pubDate = d;
}
// Now public.
public void show() {
System.out.println(title);
System.out.println(author);
System.out.println(pubDate);
}
}
// -----------------------------------------
// This class is in package mypack.
package mypack;
// Use the Book Class from bookpack.
class UseBook {
public static void main(String[] args) {
bookpack.Book[] books = new bookpack.Book[5];
books[0] = new bookpack.Book("The Art of Computer Programming, Vol 3",
"Knuth", 1973);
books[1] = new bookpack.Book("Moby Dick",
"Melville", 1851);
books[2] = new bookpack.Book("Thirteen at Dinner",
"Christie", 1933);
books[3] = new bookpack.Book("Red Storm Rising",
"Clancy", 1986);
books[4] = new bookpack.Book("On the Road",
"Kerouac", 1955);
for(int i=0; i < books.length; i++) {
books[i].show();
System.out.println();
}
}
}
// -----------------------------------------
// Make the instance variables in Book protected.
package bookpack;
public class Book {
// these are now protected
protected String title;
protected String author;
protected int pubDate;
public Book(String t, String a, int d) {
title = t;
author = a;
pubDate = d;
}
public void show() {
System.out.println(title);
System.out.println(author);
System.out.println(pubDate);
}
}
// -----------------------------------------
// Demonstrate protected.
package bookpackext;
class ExtBook extends bookpack.Book {
private String condition;
public ExtBook(String t, String a, int d, String c) {
super(t, a, d);
condition = c;
}
public void show() {
super.show();
System.out.print("Condition is " + condition);
System.out.println();
}
public String getCondition() { return condition; }
public void setCondition(String c) { condition = c; }
/* These are OK because subclass can access
a protected member. */
public String getTitle() { return title; }
public void setTitle(String t) { title = t; }
public String getAuthor() { return author; }
public void setAuthor(String a) { author = a; }
public int getPubDate() { return pubDate; }
public void setPubDate(int d) { pubDate = d; }
}
class ProtectDemo {
public static void main(String[] args) {
ExtBook[] books = new ExtBook[5];
books[0] = new ExtBook("The Art of Computer Programming, Vol 3",
"Knuth", 1973, "well used");
books[1] = new ExtBook("Moby Dick",
"Melville", 1851, "like new");
books[2] = new ExtBook("Thirteen at Dinner",
"Christie", 1933, "fair");
books[3] = new ExtBook("Red Storm Rising",
"Clancy", 1986, "good");
books[4] = new ExtBook("On the Road",
"Kerouac", 1955, "fair");
for(int i=0; i < books.length; i++) {
books[i].show();
System.out.println();
}
// Find condition of Moby Dick.
System.out.print("Condition of Moby Dick is ");
for(int i=0; i < books.length; i++)
if(books[i].getTitle() == "Moby Dick")
System.out.println(books[i].getCondition());
// books[0].title = "test title"; // Error - not accessible
}
}
// -----------------------------------------
// Demonstrate import.
package mypack;
import bookpack.*;
// Use the Book Class from bookpack.
class UseBook {
public static void main(String[] args) {
Book[] books = new Book[5];
books[0] = new Book("The Art of Computer Programming, Vol 3",
"Knuth", 1973);
books[1] = new Book("Moby Dick",
"Melville", 1851);
books[2] = new Book("Thirteen at Dinner",
"Christie", 1933);
books[3] = new Book("Red Storm Rising",
"Clancy", 1986);
books[4] = new Book("On the Road",
"Kerouac", 1955);
for(int i=0; i < books.length; i++) {
books[i].show();
System.out.println();
}
}
}
// -----------------------------------------
package owner;
public class Dog {
String name;
public Dog(String n) { name = n; }
public String toString() {
return name;
}
}
public class Owner {
String name;
Dog dog;
public Owner(String n, Dog d) {
name = n; dog = d;
}
public String toString() {
return name + " owns " + dog;
}
}
// -----------------------------------------
package dogownerdemo;
import owner.*;
class DogOwnerDemo {
public static void main(String[] args) {
Owner owner = new Owner("Fred", new Dog("Sam"));
System.out.println(owner);
}
}
// -----------------------------------------
// Find the solutions to a quadratic equation.
class Quadratic {
public static void main(String[] args) {
// a, b, and c represent the coefficients in the
// quadratic equation: ax2 + bx + c = 0
double a, b, c, x;
// Solve 4x2 + x - 3 = 0 for x.
a = 4;
b = 1;
c = -3;
// Find first solution.
x = (-b + Math.sqrt(Math.pow(b, 2) - 4 * a * c)) / (2 * a);
System.out.println("First solution: " + x);
// Find second solution.
x = (-b - Math.sqrt(Math.pow(b, 2) - 4 * a * c)) / (2 * a);
System.out.println("Second solution: " + x);
}
}
// -----------------------------------------
// Use static import to bring sqrt() and pow() into view.
import static java.lang.Math.sqrt;
import static java.lang.Math.pow;
class Quadratic {
public static void main(String[] args) {
// a, b, and c represent the coefficients in the
// quadratic equation: ax2 + bx + c = 0
double a, b, c, x;
// Solve 4x2 + x - 3 = 0 for x.
a = 4;
b = 1;
c = -3;
// Find first solution.
x = (-b + sqrt(pow(b, 2) - 4 * a * c)) / (2 * a);
System.out.println("First solution: " + x);
// Find second solution.
x = (-b - sqrt(pow(b, 2) - 4 * a * c)) / (2 * a);
System.out.println("Second solution: " + x);
}
}