《java 语言程序设计》第2章编程练习

2.1

public class test {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        double f, c;
        c = input.nextDouble();
        f = (9.0/5)*c+32;
        System.out.println(f);
    }
}

2.2

public class test {
    public static void main(String[] args) {
        double r, h;
        final double PI = 3.1415925;
        System.out.println("Enter the radius and length of a cylinder: ");
        Scanner input = new Scanner(System.in);
        r = input.nextDouble();
        h = input.nextDouble();
        System.out.println("The area is " + PI*r*r);
        System.out.println("The volume is " + PI*r*r*h);
    }
}

2.3

public class test {
    public static void main(String[] args) {
        double f, m;
        Scanner input = new Scanner(System.in);
        System.out.println("Enter a value for feet: ");
        f = input.nextDouble();
        System.out.println(f + " feet is " + 0.305 *f + " meters");
    }
}

2.4

public class test {
    public static void main(String[] args) {
        double p, k;
        Scanner input = new Scanner(System.in);
        System.out.println("Enter a number in pounds: ");
        p = input.nextDouble();
        System.out.println(p + " pounds is " + 0.454 * p + " kilograms");
    }
}

2.6

public class test {
    public static void main(String[] args) {
        int n, sum, t;
        Scanner input = new Scanner(System.in);
        System.out.println("Enter a number between 0 and 1000: ");
        n = input.nextInt();
        sum = 0;
        t = n % 10;
        while(t != 0) {
            sum += t;
            n /= 10;
            t = n % 10;
        }
        System.out.println("The sum of the digits is " + sum);
    }
}

2.7

public class test {
    public static void main(String[] args) {
        int m = 0;
        int years, days, t; 
        System.out.println("Enter the number of minutes: ");
        Scanner input = new Scanner(System.in);
        m = input.nextInt();
        t = (m / 60) / 24;
        years = t / 365;
        days = t % 365;
        System.out.println(m + " minutes is approximately " + years + " years and " + days + "days.");
    }
}

2.8

public class test {
    public static void main(String[] args) {
        int n;
        char c;
        Scanner input = new Scanner(System.in);
        System.out.print("Enter an ASCII code: ");
        n = input.nextInt();
        c = (char)n;
        System.out.println("The character for ASCII code " + n + " is " + c);
        
    }
}

2.11

public class test {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("Enter employee's name: ");
        String name = input.next();
        System.out.println("Enter number of hours worked in a week: ");
        float hours = input.nextFloat();
        System.out.println("Enter hourly pay rate: ");
        float payRate = input.nextFloat();
        System.out.println("Enter federal tax withholding rate: ");
        float ftwr = input.nextFloat();
        System.out.println("Enter state tax withholding rate: ");
        float stwr = input.nextFloat();
        System.out.println("Employee Name " + name);
        System.out.println("Hours Worked " + hours);
        System.out.println("Pay Rate: $" + payRate);
        System.out.println("Gross Pay: $" + hours * payRate);
        System.out.println("Deductions:");
        System.out.println("  Federal Withholding (" + ftwr * 100 +"%): $" + payRate * ftwr);
        System.out.println("  State Withholding (" + stwr * 100 +"%): $" + payRate * stwr);
        System.out.println("  Total Deduction: $" +  payRate * (ftwr + stwr);
    }
}

2.12

public class test {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.println("Enter balance and interest rate (e.g., 3 for 3%): ");
        double balance = input.nextDouble();
        double rate = input.nextDouble();
        System.out.printf("The interest is %.4f", balance * (rate / 1200));
    }
}

2.13

public class test {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        //System.out.println("Enter balance and interest rate (e.g., 3 for 3%): ");
        System.out.print("Enter investment amount: ");
        double investmount = input.nextDouble();
        System.out.print("Enter monthly interest rate: ");
        double rate = input.nextDouble();
        System.out.print("Enter number of years: ");
        int year = input.nextInt();
        double s = investmount * Math.pow((1 + rate / 100), (year * 12));
        System.out.println("Accumulated value is " + s);
    }
}

2.14

public class test {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter weigth in pounds: ");
        float weigth = input.nextFloat();
        System.out.print("Enter heigth in inches: ");
        float height = input.nextFloat();
        System.out.println("BMI is " + 0.45359237 * weigth / Math.pow(height * 0.0254, 2));
    }
}

2.15

public class test {
    public static void main(String[] args) {
        double t, s;
        s = t = 0;
        Scanner input = new Scanner(System.in);
        for(int i = 0; i < 6; i++) {
            s = (100 + t) * (1 + 0.00417);
            t = s;
        }
        System.out.println("After six months, result is: " + s);
    }
}

2.16

public class test {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter the amount of water in kilogram: " );
        double m = input.nextDouble();
        System.out.print("Enter the initial temperature: " );
        double it = input.nextDouble();
        System.out.print("Enter the final temperature: " );
        double ft = input.nextDouble();
        System.out.println("The energy needed is " + m * (ft - it) * 4184);
    }
}

2.17

public class test {
    public static void main(String[] args) {
        Scanner input = new Scanner(System.in);
        System.out.print("Enter the temperature in Fahrenheit: " );
        double f = input.nextDouble();
        System.out.print("Enter the wind miles per hour: ");
        double speed = input.nextDouble();
        System.out.println("The wind chill index is " + (35.74 + 0.6215 * f - 35.75 * Math.pow(speed, 0.16) + 0.427 * f * Math.pow(speed, 0.16)));
    }
}

2.18

public class test {
    public static void print() {
        System.out.print("     ");
    }
    public static void main(String[] args) {
        System.out.println("a     b     pow(a, b)");
        for(int i = 1; i < 6; i++) {
            System.out.print(i);
            print();
            System.out.print(i + 1);
            print();
            System.out.println((int)Math.pow(i, i +1));
        }
    }
}