Java语言程序设计基础篇编程练习题-第三章
3.1（代数：解一元二次方程）
import java.util.Scanner;
public class Test3_01 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter a, b, c: ");
double a = input.nextDouble();
double b = input.nextDouble();
double c = input.nextDouble();
input.close();
double criterion = b * b - 4 * a * c;
if(criterion > 0) {
double root1 = (-b + Math.pow(criterion, 0.5)) / (2 * a);
double root2 = (-b - Math.pow(criterion, 0.5)) / (2 * a);
System.out.println("The equation has two roots " + root1 + " and " + root2);
}else if(criterion == 0) {
double root = (-b + Math.pow(criterion, 0.5)) / (2 * a);
System.out.println("The equation has one root " + root);
}else {
System.out.println("The equation has no real roots");
}
}
}
3.2（游戏：三个数的加法）
import java.util.Scanner;
public class Test3_02 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
int result = 0;
double num = Math.random();
if(num < 0.5) {
//产生两个数
int num1 = (int)(Math.random() * 10);
int num2 = (int)(Math.random() * 10);
System.out.print("Enter the sum of (" + num1 + " + " + num2 + ") :");
result = num1 + num2;
}else {
//产生三个数
int num1 = (int)(Math.random() * 10);
int num2 = (int)(Math.random() * 10);
int num3 = (int)(Math.random() * 10);
System.out.print("Enter the sum of (" + num1 + " + " + num2 + " + " + num3 + ") :");
result = num1 + num2 + num3;
}
int sum = input.nextInt();
input.close();
if(sum == result) {
System.out.println("Yes");
}else {
System.out.println("No");
}
}
}
3.3（代数：求解2*2线性方程）
import java.util.Scanner;
public class Test3_03 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter a, b, c, d, e, f,: ");
double a = input.nextDouble();
double b = input.nextDouble();
double c = input.nextDouble();
double d = input.nextDouble();
double e = input.nextDouble();
double f = input.nextDouble();
input.close();
double criterion = a * d - b * c;
if(criterion == 0) {
System.out.println("The equation has no solution");
}else {
double x = (e * d - b * f) / (a * d - b * c);
double y = (a * f - e * c) / (a * d - b * c);
System.out.println("x is " + x + " and y is " + y);
}
}
}
3.4（随机月份）
import java.util.Scanner;
public class Test3_04 {
public static void main(String[] args) {
int month = (int)(Math.random() * 12 + 1);
switch(month) {
case 1:
System.out.println("January");
break;
case 2:
System.out.println("February");
break;
case 3:
System.out.println("March");
break;
case 4:
System.out.println("April");
break;
case 5:
System.out.println("May");
break;
case 6:
System.out.println("June");
break;
case 7:
System.out.println("July");
break;
case 8:
System.out.println("August");
break;
case 9:
System.out.println("September");
break;
case 10:
System.out.println("October");
break;
case 11:
System.out.println("November");
break;
case 12:
System.out.println("December");
break;
default:
System.out.println(month);
}
}
}
3.5（找到将来的日期）
import java.util.Scanner;
public class Test3_05 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter today's day: ");
int today = input.nextInt();
System.out.print("Enter the number of days elapsed since today: ");
int number = input.nextInt();
input.close();
String week = "";
switch(today) {
case 1:
week = "Monday";
break;
case 2:
week = "Tuesday";
break;
case 3:
week = "Wednesday";
break;
case 4:
week = "Thursday";
break;
case 5:
week = "Friday";
break;
case 6:
week = "Saturday";
break;
case 0:
week = "Sunday";
break;
default:
System.out.println("erro");
}
System.out.print("Today is " + week);
int next = number % 7;
today += next;
if(today > 6) {
today -= 7;
}
switch(today) {
case 1:
week = "Monday";
break;
case 2:
week = "Tuesday";
break;
case 3:
week = "Wednesday";
break;
case 4:
week = "Thursday";
break;
case 5:
week = "Friday";
break;
case 6:
week = "Saturday";
break;
case 0:
week = "Sunday";
break;
default:
System.out.println("erro");
}
System.out.println(" and the future day is " + week);
}
}
3.6（医疗应用程序：BMI）
import java.util.Scanner;
public class Test3_06 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter weight in pounds: ");
double weight = input.nextDouble();
System.out.print("Enter feet: ");//英尺
double feet = input.nextDouble();
System.out.print("Enter inches: ");//英寸 1英尺=12英寸
double inches = input.nextDouble();
input.close();
inches += feet * 12;
final double KILOGRAMS_PER_POUND = 0.45359237;
final double METERS_PER_INCH = 0.0254;
double weightInKilograms = weight * KILOGRAMS_PER_POUND;
double heightInMeters = inches * METERS_PER_INCH;
double bmi = weightInKilograms / (heightInMeters * heightInMeters);
System.out.println("BMI is " + bmi);
if(bmi < 18.5) {
System.out.println("Underweight");
}else if(bmi < 25) {
System.out.println("Normal");
}else if(bmi < 30) {
System.out.println("Overweight");
}else {
System.out.println("Obese");
}
}
}
3.7（财务应用程序，整钱兑零）
import java.util.Scanner;
public class Test3_07 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter an amount in double, for example 11.56: ");
double amount = input.nextDouble();
input.close();
int remainingAmount = (int)(amount * 100);
int numberOfOneDollars = remainingAmount / 100;
remainingAmount = remainingAmount % 100;
int numberOfQuarters = remainingAmount / 25;
remainingAmount = remainingAmount % 25;
int numberOfDimes = remainingAmount / 10;
remainingAmount = remainingAmount % 10;
int numberOfNickels = remainingAmount / 5;
remainingAmount = remainingAmount % 5;
int numberOfPennies = remainingAmount;
System.out.println("Your amount " + amount + " consists of");
if(numberOfOneDollars <= 1) {
System.out.println(" " + numberOfOneDollars + " dollar");
}else {
System.out.println(" " + numberOfOneDollars + " dollars");
}
if(numberOfQuarters <= 1) {
System.out.println(" " + numberOfQuarters + " quarter ");
}else {
System.out.println(" " + numberOfQuarters + " quarters ");
}
if(numberOfDimes <= 1) {
System.out.println(" " + numberOfDimes + " dime");
}else {
System.out.println(" " + numberOfDimes + " dimes");
}
if(numberOfNickels <= 1) {
System.out.println(" " + numberOfNickels + " nickel");
}else {
System.out.println(" " + numberOfNickels + " nickels");
}
if(numberOfPennies <= 1) {
System.out.println(" " + numberOfPennies + " pennie");
}else {
System.out.println(" " + numberOfPennies + " pennies");
}
}
}
3.8（对三个整数排序）
import java.util.Scanner;
public class Test3_08 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter a, b, c: ");
int a = input.nextInt();
int b = input.nextInt();
int c = input.nextInt();
input.close();
if(a > b) {
int t = a;
a = b;
b = t;
}
if(a > c) {
int t = a;
a = c;
c = t;
}
if(b > c) {
int t = b;
b = c;
c = t;
}
System.out.println(a + ", " + b + ", " + c);
}
}
3.9（商业，检查ISBN-10）
import java.util.Scanner;
public class Test3_09 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter the first 9 digits of an ISBN as integer: ");
String str = input.nextLine();
input.close();
int sum = 0;
for(int i = 0; i < str.length(); i++) {
sum += (int)(str.charAt(i) - '0') * (i + 1);
}
int endNumber = sum % 11;
String s = "";
switch(endNumber) {
case 0:
s = "0";
break;
case 1:
s = "1";
break;
case 2:
s = "2";
break;
case 3:
s = "3";
break;
case 4:
s = "4";
break;
case 5:
s = "5";
break;
case 6:
s = "6";
break;
case 7:
s = "7";
break;
case 8:
s = "8";
break;
case 9:
s = "9";
break;
case 10:
s = "X";
break;
default:
break;
}
str += s;
System.out.println("The ISBN-10 number is " + str);
}
}
3.10（游戏：加法检测）
import java.util.Scanner;
public class Test3_10 {
public static void main(String[] args) {
int number1 = (int)(Math.random() * 100);
int number2 = (int)(Math.random() * 100);
System.out.print("What is " + number1 + " + " + number2 + " ? ");
Scanner input = new Scanner(System.in);
int answer = input.nextInt();
input.close();
if(answer == number1 + number2) {
System.out.println("You are correct!");
}else {
System.out.println("Your answer is wrong.");
System.out.println(number1 + " + " + number2 + " should be " + (number1 + number2));
}
}
}
3.11（）
如果放在第三章，单纯使用选择语句，可以使用示例代码1。但是这种题目是有使用数组解决的方法，如示例代码2所示。
// 示例代码1
import java.util.Scanner;
public class Test3_11 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter number of years: ");
int years = input.nextInt();
System.out.print("Enter number of months: ");
int months = input.nextInt();
input.close();
boolean falg = (years % 4 == 0 && years % 100 != 0) || years % 400 == 0;
int days = 0;
String str = "";
switch(months) {
case 1:
str = "January";
days = 31;
break;
case 2:
str = ("February");
if(falg) {
days = 29;
}else {
days = 28;
}
break;
case 3:
str = ("March");
days = 31;
break;
case 4:
str = ("April");
days = 30;
break;
case 5:
str = ("May");
days = 31;
break;
case 6:
str = ("June");
days = 30;
break;
case 7:
str = ("July");
days = 31;
break;
case 8:
str = ("August");
days = 31;
break;
case 9:
str = ("September");
days = 30;
break;
case 10:
str = ("October");
days = 31;
break;
case 11:
str = ("November");
days = 30;
break;
case 12:
str = ("December");
days = 31;
break;
default:
System.out.println(months);
}
System.out.println(str + " " + years + " has " + days + " days");
}
}
// 示例代码2
import java.util.Scanner;
public class TestMonth {
public static void main(String[] args) {
String[] month = {
"", "January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"};
int[] days = {
29, 31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30, 31};
Scanner input = new Scanner(System.in);
System.out.print("Enter number of years: ");
int years = input.nextInt();
System.out.print("Enter number of months: ");
int months = input.nextInt();
input.close();
int theDays = 0;
boolean falg = (years % 4 == 0 && years % 100 != 0) || years % 400 == 0;
if (months == 2) {
if (falg) {
theDays = days[0];
} else {
theDays = days[2];
}
} else {
theDays = days[months];
}
System.out.println(month[months] + " " + years + " has " + theDays + " days");
}
}
3.12（回文数字）
import java.util.Scanner;
public class Test3_12 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.print("Enter a three-digit integer: ");
int number = input.nextInt();
input.close();
//判断是否是回文数字
int num1 = number % 10;
int num2 = number / 100;
if(num1 == num2) {
System.out.println(number + " is a palindrome");
}else {
System.out.println(number + " is not a palindrome");
}
}
}
3.13（财务应用程序，计算税款）
import java.util.Scanner;
public class Test3_13 {
public static void main(String[] args) {
Scanner input = new Scanner(System.in);
System.out.println("(0-single filer, 1-married jointly or qualifying widow(er),2-married separateiy, 3-head of household)");
System.out.print("Enter the filing status: ");
int status = input.nextInt();
System.out.print("Enter the taxable income: ");
double income = input.nextDouble();
input.close();
double tax = 0;
if(status == 0) {
if(income <= 8350) {
tax = income * 0.10;
}else if(income <= 33950) {
tax = 8350 * 0.10 + (income - 8350) * 0.15;
}else if(income <= 82250) {
tax = 8350 * 0.10 + (33950 - 8350) * 0.15 + (income - 33950) * 0.25;
}else if(income <= 171550) {
tax = 8350 * 0.10 + (33950 - 8350) * 0.15 + (82250 - 33950) * 0.25 + (income - 82250) * 0.28;
}else if(income <= 372590) {
tax = 8350 * 0.10 + (33950 - 8350) * 0.15 + (82250 - 33950) * 0.25 + (171550 - 82250) * 0.28
+ (income - 171550) * 0.33;
}else {
tax = 8350 * 0.10 + (33950 - 8350) * 0.15 + (82250 - 33950) * 0.25 + (171550 - 82250) * 0.28
+ (372950 - 171550) * 0.33 + (income - 372950) * 0.35;
}
}else if(status == 1) {
if(income <= 16700) {
tax = income * 0.10;
}else if(income <= 67900) {
tax = 16700 * 0.10 + (income - 16700) * 0.15;
}else if(income <= 137051) {
tax = 16700 * 0.10 + (67900 - 16700) * 0.15 + (income - 67900) * 0.25;
}else if(income <= 208850) {
tax = 16700 * 0.10 + (67900 - 16700) * 0.15 + (137050 - 67900) * 0.25 + (income - 137050) * 0.28;
}else if(income <= 372590) {
tax = 16700 * 0.10 + (67900 - 16700) * 0.15 + (137050 - 67900) * 0.25 + (208850 - 137050) * 0.28
+ (income - 208850) * 0.33;
}else {
tax = 16700 * 0.10 + (67900 - 16700) * 0.15 + (137050 - 67900) * 0.25 + (171550 - 137050) * 0.28
+ (372950 - 171550) * 0.33 + (income - 372950) * 0.35;
}
}else if(status ==2) {
if(income <= 8350) {
tax = income * 0.10;
}else if(income <= 33950) {
tax = 8350 * 0.10 + (income - 8350) * 0.15;
}else if(income <= 68525) {
tax = 8350 * 0.10 + (33950 - 8350) * 0.15 + (income - 33950) * 0.25;
}else if(income <= 104425) {
tax = 8350 * 0.10 + (33950 - 8350) * 0.15 + (68525 - 33950) * 0.25 + (income - 68525) * 0.28;
}else if(income <= 372590) {
tax = 8350 * 0.10 + (33950 - 8350) * 0.15 + (68525 - 33950) * 0.25 + (104425 - 68525) * 0.28
+ (income - 104425) * 0.33;
}else {
tax = 8350 * 0.10 + (33950 - 8350) * 0.15 + (68525 - 33950) * 0.25 + (104425 - 68525) * 0.28
+ (186475 - 104425) * 0.33 + (income - 186475) * 0.35;
}
}else if(status ==3) {
if(income <= 11950) {
tax = income * 0.10;
}else if(income <= 45500) {
tax = 11950 * 0.10 + (income - 11950) * 0.15;
}else if(income <= 82250) {
tax = 11950 * 0.10 + (45500 - 11950) * 0.15 + (income - 45500) * 0.25;
}else if(income <= 171550) {
tax = 11950 * 0.10 + (45500 - 11950) * 0.15 + (117450 - 45500) * 0.25 + (income - 117450) * 0.28;
}else if(income <= 372590) {
tax = 11950 * 0.10 + (45500 - 11950) * 0.15 + (117450 - 45500) * 0.25 + (171550 - 117450) * 0.28
+ (income - 171550) * 0.33;
}else {
tax = 11950 * 0.10 + (45500 - 11950) * 0.15 + (117450 - 45500) * 0.25 + (171550 - 117450) * 0.28
+ (372950 - 171550) * 0.33 + (income - 372950) * 0.35;
}
}else {
System.out.println("Error: invalid status");
System.exit(1);
}
System.out.println("Tax is " + (int)(tax * 100) / 100.0);
}
}
3.14（游戏，猜硬币正反面）
import java.util.Scanner;
public class Test3_14 {
public static void main(String[] args) {
int num = (int)(Math.random() * 2);
Scanner input = new Scanner(System.in);
System.out.print("Enter a number: ");
int guess = input.nextInt();
input.close();
if(guess == num) {
System.out.println("Yes");
}else {
System.out.println("No");
}
}
}
以上代码均为个人编写，不当之处，悉请指正。