Java语言程序设计与数据结构（基础篇）课后练习题 第九章
9.1
package demo;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
Rectangle r1 = new Rectangle(4, 40);
Rectangle r2 = new Rectangle(3.5, 35.9);
System.out.println("r1 " + r1.getWidth() + " " + r1.getHeight() + " " + r1.getArea() + " " + r1.getPerimeter());
System.out.println("r2 " + r2.getWidth() + " " + r2.getHeight() + " " + r2.getArea() + " " + r2.getPerimeter());
}
}
class Rectangle {
private double width;
private double height;
public Rectangle() {
this(1, 1);
}
public Rectangle(double w, double h) {
this.width = w;
this.height = h;
}
public double getArea() {
return width * height;
}
public double getPerimeter() {
return 2 * (width * height);
}
public double getWidth() {
return width;
}
public double getHeight() {
return height;
}
}
9.2
package demo;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
Stock stock = new Stock("ORCL","Oracle Corporation");
stock.setPreviousClosingPrice(34.5);
stock.setCurrentPrice(34.35);
System.out.println("The change percent is "+stock.getChangePercent()+"%");
}
}
class Stock {
private String symbol;
private String name;
private double previousClosingPrice;
private double currentPrice;
Stock(String symbol,String name){
this.symbol = symbol;
this.name = name;
}
public void setPreviousClosingPrice(double previousClosingPrice){
this.previousClosingPrice = previousClosingPrice;
}
public void setCurrentPrice(double price){
this.currentPrice = price;
}
public double getChangePercent(){
return (currentPrice-previousClosingPrice)/previousClosingPrice*100;
}
}
9.3
package demo;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
long seconds = 10000;
for(int i=0;i<8;i++){
java.util.Date date = new java.util.Date(seconds);
System.out.println(date.toString());
seconds *= 10;
}
}
}
9.4
package demo;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
java.util.Random random = new java.util.Random(1000);
for(int i=0;i<50;i++)
System.out.print(random.nextInt(100)+" ");
}
}
9.5
package demo;
import java.util.GregorianCalendar;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
GregorianCalendar g = new GregorianCalendar();
System.out.println(g.get(GregorianCalendar.YEAR)+"/"+g.get(GregorianCalendar.MONTH)+"/"+g.get(GregorianCalendar.DAY_OF_MONTH));
g.setTimeInMillis(1234567898765L);
System.out.println(g.get(GregorianCalendar.YEAR)+"/"+g.get(GregorianCalendar.MONTH)+"/"+g.get(GregorianCalendar.DAY_OF_MONTH));
}
}
9.6
package demo;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
StopWatch time = new StopWatch();
int[] array = new int[100000];
for (int i = 0; i < 100000; i++) {
array[i] = (int) (Math.random() * 1000000);
}
time.start();
for (int i = 0; i < array.length - 1; i++) {
int currentMin = array[i];
int currentMinIndex = i;
for (int j = i + 1; j < array.length; j++) {
if (currentMin > array[j]) {
currentMin = array[j];
currentMinIndex = j;
}
}
if (currentMinIndex != i) {
array[currentMinIndex] = array[i];
array[i] = currentMin;
}
}
time.stop();
System.out.println("timeMill: "+time.getElapsedTime()); //这里生成的是毫秒。
}
}
class StopWatch{
private long startTime;
private long endTime;
StopWatch(){
this.startTime = System.currentTimeMillis();
}
public void start(){
this.startTime = System.currentTimeMillis();
}
public void stop(){
this.endTime = System.currentTimeMillis();
}
public long getElapsedTime(){
return this.endTime-this.startTime;
}
}
9.7
package demo;
import java.util.Date;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
Account s = new Account(1122,2000);
s.setAnnualInterestRate(4.5/100);
s.withDraw(2500);
s.deposit(3000);
System.out.println("Balance: "+s.getBalance());
System.out.println("Monthly Interest: "+s.getMonthlyInterest());
System.out.println("Register Date: "+s.getDateCreated().toString());
}
}
class Account{
private int id;
private double balance;
private double annualInterestRate;
private Date dateCreated;
public Account(){
id=0;
balance=0;
annualInterestRate=0;
dateCreated=new Date();
}
public Account(int di,double b){
id=di;
balance=b;
annualInterestRate=0;
dateCreated=new Date();
}
public int getId(){
return id;
}
public void setId(int j){
id=j;
}
public double getBalance(){
return balance;
}
public void setBalance(double j){
balance=j;
}
public double getAnnualInterestRate(){
return annualInterestRate;
}
public void setAnnualInterestRate(double j){
annualInterestRate=j;
}
public Date getDateCreated(){
return dateCreated;
}
public double getMonthlyInterestRate(){
return annualInterestRate/12;
}
public double getMonthlyInterest(){
return annualInterestRate/12*balance;
}
public void withDraw(double m){
balance -= m;
}
public void deposit(double m){
balance += m;
}
}
9.8
package demo;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
Fan fan1 = new Fan();
fan1.setSpeed(Fan.FAST);
fan1.setRadius(10);
fan1.setColor("yellow");
fan1.setOn(true);
Fan fan2 = new Fan();
fan2.setSpeed(Fan.MEDIUM);
System.out.println(fan1.toString());
System.out.println(fan2.toString());
}
}
class Fan{
final static int SLOW=1;
final static int MEDIUM=2;
final static int FAST=3;
private int speed = SLOW;
private boolean on = false;
private double radius = 5;
private String color="blue";
public int getSpeed(){
return speed;
}
public void setSpeed(int s){
speed=s;
}
public boolean getOn(){
return on;
}
public void setOn(boolean j){
on=j;
}
public double getRadius(){
return radius;
}
public void setRadius(double r){
radius=r;
}
public String getColor(){
return color;
}
public void setColor(String s){
color=s;
}
public Fan(){
speed=SLOW;
on=false;
radius=5;
color="blue";
}
public String toString(){
String r="";
if(this.on)
r=r+speed+" "+color+" "+radius;
else
r=r+"fan is off "+color+" "+radius;
return r;
}
}
9.9
package demo;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
RegularPolygon p = new RegularPolygon();
RegularPolygon p2 = new RegularPolygon(6,4);
RegularPolygon p3 = new RegularPolygon(10,4,5.6,7.8);
System.out.println(p.getPerimeter()+" "+p.getArea());
System.out.println(p2.getPerimeter()+" "+p2.getArea());
System.out.println(p3.getPerimeter()+" "+p3.getArea());
}
}
class RegularPolygon{
private int n=3;
private double side=1;
private double x=0;
private double y=0;
public RegularPolygon(){
n=3;
side=1;
}
public RegularPolygon(int num,double len){
n=num;
side=len;
}
public RegularPolygon(int hum,double len,double x,double y){
n=hum;
side=len;
x=x;
y=y;
}
public void setN(int n){
n=n;
}
public int getN(){
return n;
}
public void setSide(double s){
side=s;
}
public double getSide(){
return side;
}
public void setX(double x){
x=x;
}
public double getX(){
return x;
}
public void setY(double y){
y=y;
}
public double getY(){
return y;
}
public double getPerimeter(){
return n*side;
}
public double getArea(){
return n*side*side/(4*Math.tan(Math.PI/n));
}
}
9.10
package demo;
import java.util.Scanner;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input = new Scanner(System.in);
System.out.print("Enter a b c: ");
double a = input.nextDouble();
double b = input.nextDouble();
double c = input.nextDouble();
QuadraticEquation r = new QuadraticEquation(a,b,c);
if(r.getDiscriminant()<0)
System.out.println("The equation has no roots.");
else if(r.getDiscriminant()==0)
System.out.println("One root "+r.getRoot1());
else
System.out.println("Two roots "+r.getRoot1()+" "+r.getRoot2());
}
}
class QuadraticEquation{
private double a;
private double b;
private double c;
public QuadraticEquation(double a1,double b1,double c1){
a=a1;
b=b1;
c=c1;
}
public double getA(){
return a;
}
public double getB(){
return b;
}
public double getC(){
return c;
}
public double getDiscriminant(){
return b*b-4*a*c;
}
public double getRoot1(){
return (-1*b+Math.sqrt(b*b-4*a*c))/(2*a);
}
public double getRoot2(){
return (-1*b-Math.sqrt(b*b-4*a*c))/(2*a);
}
}
9.11
package demo;
import java.util.Scanner;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
System.out.print("Enter a b c d e f: ");
Scanner input = new Scanner(System.in);
double a = input.nextDouble();
double b = input.nextDouble();
double c = input.nextDouble();
double d = input.nextDouble();
double e = input.nextDouble();
double f = input.nextDouble();
LinearEquation r = new LinearEquation(a,b,c,d,e,f);
if(r.isSolvable())
System.out.println(r.getX()+" "+r.getY());
else
System.out.println("The equation has no solutions.");
}
}
class LinearEquation{
private double a,b,c,d,e,f;
public LinearEquation(double a1,double b1,double c1,double d1,double e1,double f1){
a=a1;
b=b1;
c=c1;
d=d1;
e=e1;
f=f1;
}
public double getA(){
return a;
}
public double getB(){
return b;
}
public double getC(){
return c;
}
public double getD(){
return d;
}
public double getE(){
return e;
}
public double getF(){
return f;
}
public boolean isSolvable(){
return a*d-b*c!=0;
}
public double getX(){
return (e*d-b*f)/(a*d-b*c);
}
public double getY(){
return (a*f-e*c)/(a*d-b*c);
}
}
9.12
package demo;
import java.util.Scanner;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input = new Scanner(System.in);
System.out.print("Enter the four points x1 y1 x2 y2 x3 y3 x4 y4: ");
double x1=input.nextDouble();
double y1=input.nextDouble();
double x2=input.nextDouble();
double y2=input.nextDouble();
double x3=input.nextDouble();
double y3=input.nextDouble();
double x4=input.nextDouble();
double y4=input.nextDouble();
LinearEquation j = new LinearEquation(y1-y2,x2-x1,y3-y4,x4-x3,(y1-y2)*x1-(x1-x2)*y1,(y3-y4)*x3-(x3-x4)*y3);
if(j.isSolvable())
System.out.println(j.getX()+" "+j.getY());
else
System.out.println("No joining.");
}
}
class LinearEquation{
private double a,b,c,d,e,f;
public LinearEquation(double a1,double b1,double c1,double d1,double e1,double f1){
a=a1;
b=b1;
c=c1;
d=d1;
e=e1;
f=f1;
}
public double getA(){
return a;
}
public double getB(){
return b;
}
public double getC(){
return c;
}
public double getD(){
return d;
}
public double getE(){
return e;
}
public double getF(){
return f;
}
public boolean isSolvable(){
return a*d-b*c!=0;
}
public double getX(){
return (e*d-b*f)/(a*d-b*c);
}
public double getY(){
return (a*f-e*c)/(a*d-b*c);
}
}
9.13
package demo;
import java.util.Scanner;
public class dijiuzhang {
public static void main(String[] args) {
// TODO Auto-generated method stub
Scanner input = new Scanner(System.in);
System.out.print("Enter the number of rows and columns in the array: ");
int rows = input.nextInt();
int columns = input.nextInt();
double[][] n = new double[rows][columns];
System.out.print("Enter the array: ");
for(int i=0;imax.maxValue){
max.row=i;
max.maxValue=a[i][j];
max.column=j;
}
}
}
return max;
}
}
class Location{
public int row;
public int column;
public double maxValue;
}