《Java语言程序设计(基础篇)》(第10版 梁勇 著)第九章练习题答案

《Java语言程序设计（基础篇）》（第10版 梁勇 著）

第九章 练习题答案

9.1

public class Exercise09_01 {

public static void main(String[] args) {

MyRectangle myRectangle = new MyRectangle(4, 40);

System.out.println(\ + myRectangle.width + \ + myRectangle.height + \ + myRectangle.getArea());

System.out.println(\ + myRectangle.getPerimeter());

MyRectangle yourRectangle = new MyRectangle(3.5, 35.9); System.out.println(\ + yourRectangle.width + \ + yourRectangle.height + \ + yourRectangle.getArea());

System.out.println(\ + yourRectangle.getPerimeter()); } }

class MyRectangle { // Data members

double width = 1, height = 1;

// Constructor

public MyRectangle() { }

// Constructor

public MyRectangle(double newWidth, double newHeight) { width = newWidth; height = newHeight; }

public double getArea() { return width * height; }

public double getPerimeter() { return 2 * (width + height); } }

9.2

public class Exercise09_02 {

public static void main(String[] args) {

Stock stock = new Stock(\, \); stock.setPreviousClosingPrice(100);

// Set current price stock.setCurrentPrice(90);

// Display stock info

System.out.println(\ + stock.getPreviousClosingPrice()); System.out.println(\ + stock.getCurrentPrice());

System.out.println(\ + stock.getChangePercent() * 100 + \); } }

class Stock { String symbol; String name;

double previousClosingPrice; double currentPrice;

public Stock() { }

public Stock(String newSymbol, String newName) { symbol = newSymbol; name = newName; }

public double getChangePercent() {

return (currentPrice - previousClosingPrice) / previousClosingPrice; }

public double getPreviousClosingPrice() { return previousClosingPrice; }

public double getCurrentPrice() { return currentPrice; }

public void setCurrentPrice(double newCurrentPrice) { currentPrice = newCurrentPrice; }

public void setPreviousClosingPrice(double newPreviousClosingPrice) { previousClosingPrice = newPreviousClosingPrice; } }

9.3

public class Exercise09_03 {

public static void main(String[] args) { Date date = new Date();

int count = 1; long time = 10000;

while (count <= 8) { date.setTime(time);

System.out.println(date.toString()); count++; time *= 10; } } }

9.4

public class Exercise09_04 {

public static void main(String[] args) { Random random = new Random(1000);

for (int i = 0; i < 50; i++)

System.out.print(random.nextInt(100) + \); }