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《Java语言程序设计与数据结构》编程练习答案（第六章）（一）

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

6.1

public class book {
       public static void main(String[] args)    {
           for(int i=1;i<=100;i++)        {
               System.out.printf("%7d ",getPentagonalNumber(i));            if(i%10==0)                System.out.println("");        }    }    public static int getPentagonalNumber(int n)    {
           int tmp = n*(3*n-1)/2;        return tmp;    }}

6.2

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter an integer: ");        long dick = input.nextLong();        System.out.println("The ass of the integer is "+sumDigits(dick));    }    public static int sumDigits (long n)    {
           int sum=0;        while(n!=0)        {
               sum+=n%10;            n/=10;        }        return sum;    }}

6.3

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter a integer: ");        int pussy = input.nextInt();        if(isPalindrome(pussy))            System.out.println(pussy+" is a palindrome.");        else            System.out.println(pussy+" is not a palindrome.");    }    public static int reverse(int number)    {
           String ass = Integer.toString(number);        String dick = "";        for(int i=ass.length()-1;i>=0;i--)            dick+=ass.charAt(i);        return Integer.parseInt(dick);    }    public static boolean isPalindrome(int number)    {
           return number==reverse(number);    }}

6.4

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input = new Scanner(System.in);        System.out.print("Enter a integer: ");        int pussy = input.nextInt();        reverse(pussy);    }    public static void reverse(int number)    {
           String ass = Integer.toString(number);        String dick = "";        for(int i=ass.length()-1;i>=0;i--)            dick+=ass.charAt(i);        System.out.println(dick);    }}

6.5

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input=new Scanner(System.in);        System.out.print("Enter 3 doubles: ");        double d1=input.nextDouble();        double d2=input.nextDouble();        double d3=input.nextDouble();        displaySortedNumbers(d1,d2,d3);    }    public static void displaySortedNumbers(            double num1,double num2,double num3    )    {
           if(num1>num2)        {
               double tmp=num1;            num1=num2;            num2=tmp;        }        if(num2>num3)        {
               double tmp=num2;            num2=num3;            num3=tmp;        }        if(num1>num2)        {
               double tmp=num1;            num1=num2;            num2=tmp;        }        System.out.println(num1+" "+num2+" "+num3);    }}

6.6

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input=new Scanner(System.in);        System.out.print("Enter n: ");        int n=input.nextInt();        displayPattern(n);    }    public static void displayPattern(int n)    {
           for(int i=1;i<=n;i++)        {
               for(int j=0;j
   
    =1;j--)                System.out.printf("%3d",j);            System.out.print('\n');        }    }}
   

6.7

import java.util.Scanner;public class book {
       public static void main(String[] args)    {
           Scanner input=new Scanner(System.in);        System.out.print("The amount invested: ");        double amount = input.nextDouble();        System.out.print("Annual interest rate: ");        double ar = input.nextDouble();        System.out.println("Years    Future Value");        for(int i=1;i<=30;i++)            System.out.printf("%-2d      %9.2f\n",i,futureInvestmentValue(amount,ar/1200,i));    }    public static double futureInvestmentValue(            double investmentAmount, double monthlyInterestRate,int years    )    {
           return investmentAmount*Math.pow((1+monthlyInterestRate),years*12);    }}

6.8

public class book {
       public static void main(String[] args)    {
           System.out.println("摄氏度\t华氏度\t\t华氏度\t摄氏度");        System.out.println("------------------------------------");        for(int i=0;i<10;i++)            System.out.printf("3.1f\t%.1f\t\t%.1f\t.2f\n",(40.0-i),CF.celsiusToFahrenheit(40.0-i),(120.0-10.0*i),CF.fahrenheitToCelsius(120.0-10.0*i));    }}class CF{
       public static double celsiusToFahrenheit(double celsius)    {
           return (9.0/5)*celsius+32;    }    public static double fahrenheitToCelsius(double fahrenheit)    {
           return (5.0/9)*(fahrenheit-32);    }}

6.9

public class book {
       public static void main(String[] args)    {
           System.out.println("英尺\t 米\t\t\t 米\t     英尺");        System.out.println("-----------------------------------");        for(int i=1;i<=10;i++)            System.out.printf("%4.1f\t%.3f\t\t%.1f\t%7.3f\n",i*1.0,MM.footToMeter(i*1.0),(5.0*i+15),MM.meterToFoot(5.0*i+15));    }}class MM{
       public static double footToMeter(double foot)    {
           return 0.305*foot;    }    public static double meterToFoot(double meter)    {
           return 3.279*meter;    }}

6.10

public class book {
       public static void main(String[] args)    {
           int count=0;        for(int i=1;i<10000;i++)        {
               if(isPrime(i))                count++;        }        System.out.println("There are "+count+" primes.");    }    public static boolean isPrime(int number)    {
           for(int divisor=2;divisor<=number/2;divisor++){
               if(number%divisor==0){
                   return false;            }        }        return true;    }}

6.11

public class book {
       public static void main(String[] args)    {
           System.out.println("销售总额\t\t\t酬金");        System.out.println("-------------------");        for(int i=10000;i<=100000;i+=5000)            System.out.printf("%-6d\t\t%7.1f\n",i,computeCommission(i*1.0));    }    public static double computeCommission(double salesAmount)    {
           double ass=0;        if(salesAmount<=5000)            ass=salesAmount*0.08;        else if(salesAmount<=10000)            ass=5000*0.08+(salesAmount-5000)*0.10;        else            ass=5000*0.08+5000*0.10+(salesAmount-10000)*0.12;        return ass;    }}

6.12

public class book {
       public static void main(String[] args)    {
           printChars('1','Z',10);    }    public static void printChars(char ch1, char ch2, int numberPerLine)    {
           for(int i=1;i<=ch2-ch1+1;i++)        {
               System.out.print((char)(i+ch1-1)+" ");            if(i%numberPerLine==0)                System.out.print('\n');        }    }}

6.13

public class book {
       public static void main(String[] args)    {
           System.out.println("i\t\tm(i)");        System.out.println("--------------");        for(int i=1;i<=20;i++)            System.out.printf("%-2d\t\t%7.4f\n",i,m(i));    }    public static double m(int n)    {
           double sum=0.0;        for(int i=1;i<=n;i++)            sum+=1.0*i/(i+1);        return sum;    }}

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