《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));        }    }}