《Java语言程序设计与数据结构》编程练习答案（第五章）（四）

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

5.40

public class book {
       public static void main(String[] args)    {
           int zheng = 0;        int fan = 0;        for(int i=0;i<1000000;i++)        {
               if(Math.random()>0.5)                zheng++;            else                fan++;        }        System.out.println("正面"+zheng+"次，反面"+fan+"次");    }}

5.41

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        int max = 0;        int maxCount = 0;        System.out.print("Enter numbers: ");        while(true)        {
               int ass = input.nextInt();            if(ass==0)                break;            else            {
                   if(ass>max)                {
                       max=ass;                    maxCount=1;                }                else if(ass==max)                    maxCount++;            }        }        System.out.println("The largest number is "+max);        System.out.println("The occurrence count of the largest number is "+maxCount);    }}

5.42

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter your target: ");        final double COMMISSION_SOUGHT = input.nextDouble();        double ass = COMMISSION_SOUGHT/0.08+5000;        int i=1;        for(i=1;i
   
    =COMMISSION_SOUGHT)            {
                   System.out.println("You need to sell $"+i);                break;            }        }    }}

5.43

public class book {
       public static void main(String[] args)    {
           int count = 0;        for(int i=1;i<=6;i++)            for(int j=i+1;j<=7;j++)            {
                   System.out.printf("%d  %d\n",i,j);                count++;            }        System.out.println("The total number of all combinations is "+count);    }}

5.44

黑人问号

5.45

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input=new Scanner(System.in);        double sum = 0;        double sumQ = 0;        System.out.print("Enter 10 numbers: ");        for(int i=0;i<10;i++)        {
               double tmp=input.nextDouble();            sum+=tmp;            sumQ+=tmp*tmp;        }        double means = sum/10.0;        double sd = Math.sqrt((sumQ-sum*sum/10.0)/9.0);        System.out.println("The mean is "+means);        System.out.println("The standard deviation is "+sd);    }}

5.46

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter a string: ");        String ass = input.nextLine();        System.out.print("The reversed string is ");        for(int i=ass.length()-1;i>=0;i--)            System.out.print(ass.charAt(i));        System.out.print('\n');    }}

5.47

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 12 digits:");        String ass = input.nextLine();        if(ass.length()!=12)            System.out.println(ass+" is invalid.");        else        {
               int sum=0;            for(int i=0;i<12;i++)            {
                   int tmp = ass.charAt(i)-'0';                if(i%2==1)                    sum+=tmp;                else                    sum+=3*tmp;            }            int tail = 10-sum%10;            if(tail==10)                tail=0;            System.out.println("The ISBN-13 number is "+ass+tail);        }    }}

5.48

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.nextLine();        int len = ass.length();        for(int i=0;i

5.49

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.nextLine();        int len = ass.length();        ass=ass.toLowerCase();        int countV =0;        int countC = 0;        for(int i=0;i

5.50

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.nextLine();        int len = ass.length();        int countC = 0;        for(int i=0;i
   
    = 'A' && ass.charAt(i) <= 'Z')                countC++;        }        System.out.println("The number of upper case letter is "+countC);    }}

5.51

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           System.out.print("Enter the first string: ");        Scanner input = new Scanner(System.in);        String ass = input.nextLine();        System.out.print("Enter the second string: ");        String dick = input.nextLine();        int len1 = ass.length();        int len2 = dick.length();        int range = Math.min(len1,len2);        if(ass.charAt(0)!=dick.charAt(0))            System.out.println(ass+" and "+dick+" have no common prefix");        else {
               System.out.print("The common prefix is ");            for (int i = 0; i < range; i++) {
                   if (ass.charAt(i) == dick.charAt(i))                    System.out.print(ass.charAt(i));            }            System.out.println("");        }    }}