《Java语言程序设计与数据结构》编程练习答案（第四章）（二）

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

4.14

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 grade: ");        char ass = input.nextLine().charAt(0);        if(ass<='F'&&ass>='A')            System.out.printf("The numeric value for grade %c is %d\n",ass,4-ass+'A');        else            System.out.printf("%c is an invalid grade\n",ass);    }}

4.15

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<='c'&&ass>='a')||(ass<='C'&&ass>='A'))            System.out.println("The corresponding number is 2");        else if((ass<='f'&&ass>='d')||(ass<='F'&&ass>='D'))            System.out.println("The corresponding number is 3");        else if((ass<='i'&&ass>='g')||(ass<='I'&&ass>='G'))            System.out.println("The corresponding number is 4");        else if((ass<='l'&&ass>='j')||(ass<='L'&&ass>='J'))            System.out.println("The corresponding number is 5");        else if((ass<='o'&&ass>='m')||(ass<='O'&&ass>='M'))            System.out.println("The corresponding number is 6");        else if((ass<='s'&&ass>='p')||(ass<='S'&&ass>='P'))            System.out.println("The corresponding number is 7");        else if((ass<='v'&&ass>='t')||(ass<='V'&&ass>='T'))            System.out.println("The corresponding number is 8");        else if((ass<='z'&&ass>='w')||(ass<='Z'&&ass>='W'))            System.out.println("The corresponding number is 9");        else            System.out.println(ass+" is an invalid input");    }}

4.16

public static void main(String[] args)    {        int ass = (int)'A'+(int)(Math.random()*26);        char dick = (char)ass;        System.out.printf("The random letter is %c\n",dick);    }}

4.17

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter a year: ");        int year = input.nextInt();        System.out.print("Enter a month: ");        String month = input.next();        boolean isLeapYear = (year%4==0&&year%100!=0)||(year%400==0);        int days = 0;        if(month.equals("Jan")||month.equals("Mar")||month.equals("May")||month.equals("Jul")||month.equals("Aug")||month.equals("Oct")||month.equals("Dec"))            days=31;        else if(month.equals("Apr")||month.equals("Jun")||month.equals("Sep")||month.equals("Nov"))            days=30;        else if(month.equals("Feb")&&isLeapYear)            days=29;        else if(month.equals("Feb")&&!isLeapYear)            days=28;        else            days=0;        if(days!=0)            System.out.printf("%s %d has %d days\n",month,year,days);        else            System.out.printf("%s is not a correct month name",month);    }}

4.18

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter two characters: ");        String ass = input.next();        char d1 = ass.charAt(0);        char d2 = ass.charAt(1);        String dept = "";        String grade = "";        if((d1=='M'||d1=='C'||d1=='I')&&(d2>='1'&&d2<='4'))        {
               if(d1=='M')                dept="Mathematics";            else if(d1=='C')                dept="Computer science";            else                dept="IT";            if(d2=='1')                grade="Freshman";            else                grade="Junior";            System.out.printf("%s %s\n",dept,grade);        }        else            System.out.println("Invalid input");    }}

4.19

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the first 9 digits of an ISBN as String: ");        String ass = input.next();        int sum=0;        for(int i=1;i<=9;i++)            sum+=(ass.charAt(i-1)-'0')*i;        int tail = sum%11;        if(tail==10)            ass=ass+"X";        else            ass=ass+tail;        System.out.println("The ISBN-10 number is "+ass);    }}

4.20

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

4.21

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           System.out.print("Enter a SSN: ");        Scanner input = new Scanner(System.in);        String ass = input.next();        boolean valid = true;        if(ass.length()!=11)            valid=false;        else        {
               for(int i=0;i<=2;i++)                valid=valid&&(ass.charAt(i)>='0'&&ass.charAt(i)<='9');            valid=valid&&(ass.charAt(3)=='-');            for(int i=4;i<=5;i++)                valid=valid&&(ass.charAt(i)>='0'&&ass.charAt(i)<='9');            valid=valid&&(ass.charAt(6)=='-');            for(int i=7;i<=10;i++)                valid=valid&&(ass.charAt(i)>='0'&&ass.charAt(i)<='9');        }        if(valid)            System.out.println(ass+" is a valid SSN");        else            System.out.println(ass+" is an invalid SSN");    }}

4.22

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter string s1: ");        String s1 = input.next();        System.out.print("Enter string s2: ");        String s2 = input.next();        if(s1.contains(s2))            System.out.println(s2+" is a substring of "+s1);        else            System.out.println(s2+" is not a substring of "+s1);    }}

4.23

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter employee's name: ");        String name = input.next();        System.out.print("Enter number of hours worked in a week: ");        double hour = input.nextDouble();        System.out.print("Enter hourly pay rate: ");        double payRate = input.nextDouble();        System.out.print("Enter federal tax withholding rate: ");        double ftax = input.nextDouble();        System.out.print("Enter state tax withholding rate: ");        double stax = input.nextDouble();        System.out.printf("Employee name: %s\n",name);        System.out.printf("Hours worked: %.2f\nPay Rate: $%.2f\nGross Pay: $%.2f\n",hour,payRate,hour*payRate);        System.out.printf("Deductions:\n  Federal Withholding (%f%%): $%.2f\n  State Withholding (%f%%): $%.2f\n  Total Deduction: $%.2f\n",ftax*100,ftax*hour*payRate,stax*100,stax*hour*payRate,ftax*hour*payRate+stax*hour*payRate);        System.out.printf("Net Pay: $%.2f\n",hour*payRate*(1-ftax-stax));    }}

4.24

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter the first city: ");        String ass1 = input.nextLine();        System.out.print("Enter the second city: ");        String ass2 = input.nextLine();        System.out.print("Enter the third city: ");        String ass3 = input.nextLine();        if(ass1.compareTo(ass2)>0)        {
               String ass0 = ass1;            ass1 = ass2;            ass2 = ass0;        }        if(ass2.compareTo(ass3)>0)        {
               String ass0 = ass2;            ass2 = ass3;            ass3 = ass0;        }        if(ass1.compareTo(ass2)>0)        {
               String ass0 = ass1;            ass1 = ass2;            ass2 = ass0;        }        System.out.printf("The three cities in alphabetical order are %s %s %s",ass1,ass2,ass3);    }}

4.25

public class book {
       public static void main(String[] args)    {
           String ass = "";        for(int i=0;i<3;i++)            ass += (char)((int)('A'+Math.random()*26));        for(int i=0;i<4;i++)            ass+=(char)('0'+Math.random()*10);        System.out.println("The AV-code is "+ass);    }}

4.26

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter an amount in string, for example 114.514: ");        String rawMoney = input.next();        int remains = 0;        int dot = rawMoney.indexOf('.');        if(dot==-1)            remains=Integer.parseInt(rawMoney)*100;        else        {
               int dollars=Integer.parseInt(rawMoney.substring(0,dot));            int cents = 0;            if(rawMoney.length()-dot==1)                cents=10*Integer.parseInt(rawMoney.substring(dot+1));            else                cents=Integer.parseInt(rawMoney.substring(dot+1,dot+3));            remains=dollars*100+cents;        }        int numdoll = remains/100;        remains=remains%100;        int numqua = remains/25;        remains=remains%25;        int numdi = remains/10;        remains = remains%10;        int numni = remains/5;        remains = remains%5;        int nump = remains;        System.out.println("Your amount "+rawMoney+" consists of");        System.out.println("    "+numdoll+" dollars");        System.out.println("    "+numqua+" quarters");        System.out.println("    "+numdi+" dimes");        System.out.println("    "+numni+" nickels");        System.out.println("    "+nump+" pennies");    }}