Example 2

Chapter 2

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public class ComputeArea {
  public static void main(String[] args) {
    double radius; // Declare radius
    double area; // Declare area

    // Assign a radius
    radius = 20; // New value is radius

    // Compute area
    area = radius * radius * 3.14159;

    // Display results
    System.out.println("The area for the circle of radius " +
      radius + " is " + area);
  }
}

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import java.util.Scanner; // Scanner is in the java.util package

public class ComputeAreaWithConsoleInput {
  public static void main(String[] args) {
    // Create a Scanner object
    Scanner input = new Scanner(System.in);
   
    // Prompt the user to enter a radius
    System.out.print("Enter a number for radius: ");
    double radius = input.nextDouble();

    // Compute area
    double area = radius * radius * 3.14159;

    // Display result
    System.out.println("The area for the circle of radius " +
      radius + " is " + area);
  }
}

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import java.util.Scanner; // Scanner is in the java.util package

public class ComputeAverage {
  public static void main(String[] args) {
    // Create a Scanner object
    Scanner input = new Scanner(System.in);
   
    // Prompt the user to enter three numbers
    System.out.print("Enter three numbers: ");
    double number1 = input.nextDouble();
    double number2 = input.nextDouble();
    double number3 = input.nextDouble();

    // Compute average
    double average = (number1 + number2 + number3) / 3;

    // Display result
    System.out.println("The average of " + number1 + " " + number2
      + " " + number3 + " is " + average);
  }
}

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import java.util.Scanner; // Scanner is in the java.util package

public class ComputeAreaWithConstant {
  public static void main(String[] args) {
    final double PI = 3.14159; // Declare a constant
   
    // Create a Scanner object
    Scanner input = new Scanner(System.in);
   
    // Prompt the user to enter a radius
    System.out.print("Enter a number for radius: ");
    double radius = input.nextDouble();

    // Compute area
    double area = radius * radius * PI;

    // Display result
    System.out.println("The area for the circle of radius " +
      radius + " is " + area);
  }
}

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import java.util.Scanner;

public class DisplayTime {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    // Prompt the user for input
    System.out.print("Enter an integer for seconds: ");
    int seconds = input.nextInt();

    int minutes = seconds / 60; // Find minutes in seconds
    int remainingSeconds = seconds % 60; // Seconds remaining
    System.out.println(seconds + " seconds is " + minutes +
      " minutes and " + remainingSeconds + " seconds");
  }
}

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import java.util.Scanner;

public class FahrenheitToCelsius {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);

    System.out.print("Enter a degree in Fahrenheit: ");
    double fahrenheit = input.nextDouble();

    // Convert Fahrenheit to Celsius
    double celsius = (5.0 / 9) * (fahrenheit - 32);
    System.out.println("Fahrenheit " + fahrenheit + " is " +
      celsius + " in Celsius");
  }
}

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public class ShowCurrentTime {
  public static void main(String[] args) {
    // Obtain the total milliseconds since midnight, Jan 1, 1970
    long totalMilliseconds = System.currentTimeMillis();

    // Obtain the total seconds since midnight, Jan 1, 1970
    long totalSeconds = totalMilliseconds / 1000;

    // Compute the current second in the minute in the hour
    long currentSecond = totalSeconds % 60;

    // Obtain the total minutes
    long totalMinutes = totalSeconds / 60;

    // Compute the current minute in the hour
    long currentMinute = totalMinutes % 60;

    // Obtain the total hours
    long totalHours = totalMinutes / 60;

    // Compute the current hour
    long currentHour = totalHours % 24;

    // Display results
    System.out.println("Current time is " + currentHour + ":"
      + currentMinute + ":" + currentSecond + " GMT");
  }
}

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import java.util.Scanner;

public class SalesTax {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);

    System.out.print("Enter purchase amount: ");
    double purchaseAmount = input.nextDouble();
   
    double tax = purchaseAmount * 0.06;
    System.out.println("Sales tax is " + (int)(tax * 100) / 100.0);
  }
}

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import java.util.Scanner;

public class ComputeLoan {
  public static void main(String[] args) {  
    // Create a Scanner
    Scanner input = new Scanner(System.in);

    // Enter yearly interest rate
    System.out.print("Enter yearly interest rate, for example 8.25: ");
    double annualInterestRate = input.nextDouble();
   
    // Obtain monthly interest rate
    double monthlyInterestRate = annualInterestRate / 1200;

    // Enter number of years
    System.out.print(
      "Enter number of years as an integer, for example 5: ");
    int numberOfYears = input.nextInt();
   
    // Enter loan amount
    System.out.print("Enter loan amount, for example 120000.95: ");
    double loanAmount = input.nextDouble();
   
    // Calculate payment
    double monthlyPayment = loanAmount * monthlyInterestRate / (1
      - 1 / Math.pow(1 + monthlyInterestRate, numberOfYears * 12));
    double totalPayment = monthlyPayment * numberOfYears * 12;

    // Display results
    System.out.println("The monthly payment is $" +
      (int)(monthlyPayment * 100) / 100.0);
    System.out.println("The total payment is $" +
      (int)(totalPayment * 100) / 100.0);
  }
}

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import java.util.Scanner;

public class ComputeChange {
  public static void main(String[] args) {  
    // Create a Scanner
    Scanner input = new Scanner(System.in);

    // Receive the amount
    System.out.print(
      "Enter an amount in double, for example 11.56: ");
    double amount = input.nextDouble();

    int remainingAmount = (int)(amount * 100);

    // Find the number of one dollars
    int numberOfOneDollars = remainingAmount / 100;
    remainingAmount = remainingAmount % 100;

    // Find the number of quarters in the remaining amount
    int numberOfQuarters = remainingAmount / 25;
    remainingAmount = remainingAmount % 25;

    // Find the number of dimes in the remaining amount
    int numberOfDimes = remainingAmount / 10;
    remainingAmount = remainingAmount % 10;

    // Find the number of nickels in the remaining amount
    int numberOfNickels = remainingAmount / 5;
    remainingAmount = remainingAmount % 5;

    // Find the number of pennies in the remaining amount
    int numberOfPennies = remainingAmount;

    // Display results
    System.out.println("Your amount " + amount + " consists of");
    System.out.println("    " + numberOfOneDollars + " dollars");
    System.out.println("    " + numberOfQuarters + " quarters ");
    System.out.println("    " + numberOfDimes + " dimes");
    System.out.println("    " + numberOfNickels + " nickels");
    System.out.println("    " + numberOfPennies + " pennies");
  }
}

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