《Java语言程序设计与数据结构》编程练习答案（第四章）（一）

英文名：Introduction to Java Programming and Data Structures, Comprehensive Version, 11th Edition

4.1

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           System.out.print("Enter the length from the center to a vertex: ");        Scanner input = new Scanner(System.in);        final double PI = 3.141592654;        double r = input.nextDouble();        double s = 2*r*Math.sin(PI/5);        double a = 5*s*s/(4*Math.tan(PI/5));        System.out.printf("The area of the pentagon is %.2f",a);    }}

4.2

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter point 1 (latitude and longitude) in degrees: ");        double x1 = input.nextDouble();        double y1 = input.nextDouble();        System.out.print("Enter point 2 (latitude and longitude) in degrees: ");        double x2 = input.nextDouble();        double y2 = input.nextDouble();        double d = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));        System.out.println("The distance between the two points is "+d+" km");    }}

4.3

public class book {
       public static void main(String[] args)    {
           double x1 = 35.2270869;        double y1 = -80.8431267;        double x2 = 32.0835407;        double y2 = -81.0998342;        double dcs = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));        x2 = 33.7489954;        y2 = -84.3879824;        double dca = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));        x1 = 28.5383355;        y1 = -81.3792365;        double doa = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));        x2 = 32.0835407;        y2 = -81.0998342;        double dos = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));        x1 = 33.7489954;        y1 = -84.0998342;        double das = 6371.0*Math.acos(Math.sin(Math.toRadians(x1))*Math.sin(Math.toRadians(x2))+Math.cos(Math.toRadians(x1))*Math.cos(Math.toRadians(x2))*Math.cos(Math.toRadians(y1-y2)));        double s1 = (dca+dcs+das)/2;        double s2 = (doa+dos+das)/2;        double a = Math.sqrt(s1*(s1-dca)*(s1-dcs)*(s1-das))+Math.sqrt(s2*(s2-doa)*(s2-dos)*(s2-das));        System.out.println("The area is "+a+" km^2");    }}

4.4

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           final double PI = 3.141592654;        Scanner input = new Scanner(System.in);        System.out.print("Enter the side: ");        double s = input.nextDouble();        double a = 6*s*s/(4*Math.tan(PI/6));        System.out.println("The area of the hexagon is "+a);    }}

4.5

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           final double PI = 3.141592654;        Scanner input = new Scanner(System.in);        System.out.print("Enter the number of sides: ");        int n = input.nextInt();        System.out.print("Enter the side: ");        double s = input.nextDouble();        double a = n*s*s/(4*Math.tan(PI/n));        System.out.println("The area of the polygon is "+a);    }}

4.6

public class book {
       public static void main(String[] args)    {
           final double PI = 3.141592654;        double alpha1 = Math.random()*2*PI;        double alpha2 = Math.random()*2*PI;        double alpha3 = Math.random()*2*PI;        double x1 = 40*Math.cos(alpha1);        double y1 = 40*Math.sin(alpha1);        double x2 = 40*Math.cos(alpha2);        double y2 = 40*Math.sin(alpha2);        double x3 = 40*Math.cos(alpha3);        double y3 = 40*Math.sin(alpha3);        double a = Math.sqrt((x1-x2)*(x1-x2)+(y1-y2)*(y1-y2));        double b = Math.sqrt((x2-x3)*(x2-x3)+(y2-y3)*(y2-y3));        double c = Math.sqrt((x1-x3)*(x1-x3)+(y1-y3)*(y1-y3));        double aa = Math.toDegrees(Math.acos((a*a-b*b-c*c)/(-2*b*c)));        double ab = Math.toDegrees(Math.acos((b*b-a*a-c*c)/(-2*a*c)));        double ac = Math.toDegrees(Math.acos((c*c-b*b-a*a)/(-2*a*b)));        System.out.println("The three angles are: "+aa+" "+ab+" "+ac);    }}

4.7

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           final double PI = 3.141592654;        Scanner input = new Scanner(System.in);        System.out.print("Enter the radius of the bounding circle: ");        double r = input.nextDouble();        double base = 0.1*PI;        System.out.println("The coordinates of fibe points on the pentagon are");        for(int i=0;i<5;i++)        {
               System.out.printf("(%.2f, %.2f)%n",r*Math.cos(base),r*Math.sin(base));            base+=0.4*PI;        }    }}

4.8

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Ent6er an ASCII code: ");        int ass = input.nextInt();        char dick = (char)ass;        System.out.printf("The character for ASCII code %d is %c",ass,dick);    }}

4.9

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter a character: ");        String jb = input.nextLine();        char ass = jb.charAt(0);        int dick = (int)ass;        System.out.printf("The Unicode for the character %c is %d",ass,dick);    }}

4.10

public class book {
       public static void main(String[] args)    {
           //原来代码中        // int answer = input.nextInt()--->char answer = input.nextLine().charAt(0)        // if(answer==1)--->if(answer=='Y')    }}

4.11

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           System.out.print("Enter a decimal value (0 to 15): ");        Scanner input = new Scanner(System.in);        int ass = input.nextInt();        if(ass>=0&&ass<=15){
               if(ass<10)                System.out.printf("The hex value is %d",ass);            else                System.out.printf("The hex value is %c",'A'+ass-10);        }        else            System.out.printf("%d is an invalid input",ass);    }}

4.12

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           String[] bins = {
   "0","1","10","11","100","101","110","111","1000","1001","1010","1011","1100","1101","1110","1111"};        System.out.print("Enter a hex digit: ");        Scanner input = new Scanner(System.in);        char ass = input.nextLine().charAt(0);        if(ass>='0'&&ass<='9')            System.out.printf("The binary value is %s\n",bins[ass-'0']);        else if(ass>='A'&&ass<='F')            System.out.printf("The binary value is %s\n",bins[ass-'A'+10]);        else            System.out.printf("%c is an invalid input\n",ass);    }}

4.13

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter a letter: ");        char ass = input.nextLine().charAt(0);        if((ass<='z'&&ass>='a')||(ass<='Z'&&ass>='A'))        {
               if(ass=='a'||ass=='e'||ass=='i'||ass=='o'||ass=='u'            ||ass=='A'||ass=='E'||ass=='I'||ass=='O'||ass=='U')                System.out.println(ass+" is a vowel");            else                System.out.println(ass+" is a consonant");        }        else            System.out.println(ass+" is an invalid input");    }}

转载地址：http://gkwai.baihongyu.com/

你可能感兴趣的文章