《Java语言程序设计与数据结构》编程练习答案（第六章）（一）

《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<n-i;j++)
                System.out.print("   ");
            for(int j=i;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;
    }
}