Example 4

Chapter 4

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import java.util.Scanner;

public class ComputeAngles {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
   
    // Prompt the user to enter three points
    System.out.print("Enter three points: ");
    double x1 = input.nextDouble();
    double y1 = input.nextDouble();
    double x2 = input.nextDouble();
    double y2 = input.nextDouble();
    double x3 = input.nextDouble();
    double y3 = input.nextDouble();
   
    // Compute three sides
    double a = Math.sqrt((x2 - x3) * (x2 - x3)
        + (y2 - y3) * (y2 - y3));
    double b = Math.sqrt((x1 - x3) * (x1 - x3)
        + (y1 - y3) * (y1 - y3));
    double c = Math.sqrt((x1 - x2) * (x1 - x2)
        + (y1 - y2) * (y1 - y2));
   
    // Compute three angles
    double A = Math.toDegrees(Math.acos((a * a - b * b - c * c)
        / (-2 * b * c)));
    double B = Math.toDegrees(Math.acos((b * b - a * a - c * c)
        / (-2 * a * c)));
    double C = Math.toDegrees(Math.acos((c * c - b * b - a * a)
        / (-2 * a * b)));
   
    // Display results
    System.out.println("The three angles are " +
        Math.round(A * 100) / 100.0 + " " +
        Math.round(B * 100) / 100.0 + " " +
        Math.round(C * 100) / 100.0);
  }
}

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import java.util.Scanner;

public class OrderTwoCities {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
   
    // Prompt the user to enter two cities
    System.out.print("Enter the first city: ");
    String city1 = input.nextLine();
    System.out.print("Enter the second city: ");
    String city2 = input.nextLine();
   
    if (city1.compareTo(city2) < 0)
      System.out.println("The cities in alphabetical order are " +
         city1 + " " + city2);
    else
      System.out.println("The cities in alphabetical order are " +
          city2 + " " + city1);
  }
}

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import java.util.Scanner;

public class GuessBirthday {
  public static void main(String[] args) {
    String set1 =
      " 1  3  5  7\n" +
      " 9 11 13 15\n" +
      "17 19 21 23\n" +
      "25 27 29 31";

    String set2 =
      " 2  3  6  7\n" +
      "10 11 14 15\n" +
      "18 19 22 23\n" +
      "26 27 30 31";

    String set3 =
      " 4  5  6  7\n" +
      "12 13 14 15\n" +
      "20 21 22 23\n" +
      "28 29 30 31";

    String set4 =
      " 8  9 10 11\n" +
      "12 13 14 15\n" +
      "24 25 26 27\n" +
      "28 29 30 31";

    String set5 =
      "16 17 18 19\n" +
      "20 21 22 23\n" +
      "24 25 26 27\n" +
      "28 29 30 31";

    int day = 0;

    // Create a Scanner
    Scanner input = new Scanner(System.in);

    // Prompt the user to answer questions
    System.out.print("Is your birthday in Set1?\n");
    System.out.print(set1);
    System.out.print("\nEnter 0 for No and 1 for Yes: ");
    int answer = input.nextInt();

    if (answer == 1)
      day += 1;

    // Prompt the user to answer questions
    System.out.print("\nIs your birthday in Set2?\n");
    System.out.print(set2);
    System.out.print("\nEnter 0 for No and 1 for Yes: ");
    answer = input.nextInt();

    if (answer == 1)
      day += 2;

    // Prompt the user to answer questions
    System.out.print("Is your birthday in Set3?\n");
    System.out.print(set3);
    System.out.print("\nEnter 0 for No and 1 for Yes: ");
    answer = input.nextInt();

    if (answer == 1)
      day += 4;

    // Prompt the user to answer questions
    System.out.print("\nIs your birthday in Set4?\n");
    System.out.print(set4);
    System.out.print("\nEnter 0 for No and 1 for Yes: ");
    answer = input.nextInt();

    if (answer == 1)
      day += 8;

    // Prompt the user to answer questions
    System.out.print("\nIs your birthday in Set5?\n");
    System.out.print(set5);
    System.out.print("\nEnter 0 for No and 1 for Yes: ");
    answer = input.nextInt();

    if (answer == 1)
      day += 16;

    System.out.println("\nYour birthday is " + day + "!");
  }
}

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import java.util.Scanner;

public class HexDigit2Dec {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.print("Enter a hex digit: ");
    String hexString = input.nextLine();
   
    // Check if the hex string has exactly one character
    if (hexString.length() != 1) {
      System.out.println("You must enter exactly one character");
      System.exit(1);
    }
   
    // Display decimal value for the hex digit
    char ch = Character.toUpperCase(hexString.charAt(0));  
    if (ch <= 'F' && ch >= 'A') {
      int value = ch - 'A' + 10;
      System.out.println("The decimal value for hex digit "
        + ch + " is " + value);
    }
    else if (Character.isDigit(ch)) {
      System.out.println("The decimal value for hex digit "
        + ch + " is " + ch);
    }
    else {
      System.out.println(ch + " is an invalid input");
    }
  }
}

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import java.util.Scanner;

public class LotteryUsingStrings {
  public static void main(String[] args) {
    // Generate a lottery as a two-digit string
    String lottery = "" + (int)(Math.random() * 10)
      + (int)(Math.random() * 10);

    // Prompt the user to enter a guess
    Scanner input = new Scanner(System.in);
    System.out.print("Enter your lottery pick (two digits): ");
    String guess = input.nextLine();

    // Get digits from lottery
    int lotteryDigit1 = lottery.charAt(0);
    int lotteryDigit2 = lottery.charAt(1);

    // Get digits from guess
    int guessDigit1 = guess.charAt(0);
    int guessDigit2 = guess.charAt(1);

    System.out.println("The lottery number is " + lottery);

    // Check the guess
    if (guess.equals(lottery))
      System.out.println("Exact match: you win $10,000");
    else if (guessDigit2 == lotteryDigit1
          && guessDigit1 == lotteryDigit2)
      System.out.println("Match all digits: you win $3,000");
    else if (guessDigit1 == lotteryDigit1
          || guessDigit1 == lotteryDigit2
          || guessDigit2 == lotteryDigit1
          || guessDigit2 == lotteryDigit2)
      System.out.println("Match one digit: you win $1,000");
    else
      System.out.println("Sorry, no match");
  }
}

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public class FormatDemo {
  public static void main(String[] args) {
    // Display the header of the table
    System.out.printf("%-10s%-10s%-10s%-10s%-10s\n", "Degrees",
      "Radians", "Sine", "Cosine", "Tangent");

    // Display values for 30 degrees
    int degrees = 30;
    double radians = Math.toRadians(degrees);
    System.out.printf("%-10d%-10.4f%-10.4f%-10.4f%-10.4f\n", degrees,
      radians, Math.sin(radians), Math.cos(radians),
      Math.tan(radians));

    // Display values for 60 degrees
    degrees = 60;
    radians = Math.toRadians(degrees);
    System.out.printf("%-10d%-10.4f%-10.4f%-10.4f%-10.4f\n", degrees,
      radians, Math.sin(radians), Math.cos(radians),
      Math.tan(radians));
  }
}

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