Selections - examples from Liang Intro to Java Comprehensive 10e

AdditionQuiz.java

import java.util.Scanner;

public class AdditionQuiz {
  public static void main(String[] args) {
    int number1 = (int)(System.currentTimeMillis() % 10);
    int number2 = (int)(System.currentTimeMillis() / 7 % 10);

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

    System.out.print(
      "What is " + number1 + " + " + number2 + "? ");

    int answer = input.nextInt();

    System.out.println(
      number1 + " + " + number2 + " = " + answer + " is " +
      (number1 + number2 == answer));
  }
}

ChineseZodiac.java

import java.util.Scanner;

public class ChineseZodiac {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    
    System.out.print("Enter a year: ");
    int year = input.nextInt();
    
    switch (year % 12) {
      case 0: System.out.println("monkey"); break;
      case 1: System.out.println("rooster"); break;
      case 2: System.out.println("dog"); break;
      case 3: System.out.println("pig"); break;
      case 4: System.out.println("rat"); break;
      case 5: System.out.println("ox"); break;
      case 6: System.out.println("tiger"); break;
      case 7: System.out.println("rabbit"); break;
      case 8: System.out.println("dragon"); break;
      case 9: System.out.println("snake"); break;
      case 10: System.out.println("horse"); break;
      case 11: System.out.println("sheep"); break;
    }
  }
}

ComputeAndInterpretBMI.java

import java.util.Scanner;

public class ComputeAndInterpretBMI {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    
    // Prompt the user to enter weight in pounds
    System.out.print("Enter weight in pounds: ");
    double weight = input.nextDouble();
    
    // Prompt the user to enter height in inches
    System.out.print("Enter height in inches: ");
    double height = input.nextDouble();
    
    final double KILOGRAMS_PER_POUND = 0.45359237; // Constant
    final double METERS_PER_INCH = 0.0254; // Constant 
    
    // Compute BMI
    double weightInKilograms = weight * KILOGRAMS_PER_POUND; 
    double heightInMeters = height * METERS_PER_INCH; 
    double bmi = weightInKilograms / 
      (heightInMeters * heightInMeters);

    // Display result
    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");
  }
}

ComputeTax.java

import java.util.Scanner; 

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

    // Prompt the user to enter filing status
    System.out.print("(0-single filer, 1-married jointly or " +
      "qualifying widow(er), 2-married separately, 3-head of " +
      "household) Enter the filing status: ");
    int status = input.nextInt();

    // Prompt the user to enter taxable income
    System.out.print("Enter the taxable income: ");
    double income = input.nextDouble();

    // Compute tax
    double tax = 0;

    if (status == 0) { // Compute tax for single filers
      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 <= 372950)
        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) { // Compute tax for married file jointly
      // Left as exercise
    }
    else if (status == 2) { // Compute tax for married separately
      // Left as exercise
    }
    else if (status == 3) { // Compute tax for head of household
      // Left as exercise
    }
    else {
      System.out.println("Error: invalid status");
      System.exit(1);
    }

    // Display the result
    System.out.println("Tax is " + (int)(tax * 100) / 100.0);
  }
}

LeapYear.java

import java.util.Scanner; 

public class LeapYear {
  public static void main(String args[]) {
    // Create a Scanner
    Scanner input = new Scanner(System.in);
    System.out.print("Enter a year: ");
    int year = input.nextInt();

    // Check if the year is a leap year 
    boolean isLeapYear = 
      (year % 4 == 0 && year % 100 != 0) || (year % 400 == 0);

    // Display the result in a message dialog box
    System.out.println(year + " is a leap year? " + isLeapYear);   
  } 
}

Lottery.java

import java.util.Scanner;

public class Lottery {
  public static void main(String[] args) {
    // Generate a lottery
    int lottery = (int)(Math.random() * 100);

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

    // Get digits from lottery
    int lotteryDigit1 = lottery / 10;
    int lotteryDigit2 = lottery % 10;

    // Get digits from guess
    int guessDigit1 = guess / 10;
    int guessDigit2 = guess % 10;

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

    // Check the guess
    if (guess == 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"); 
  }
}

SimpleIfDemo.java

import java.util.Scanner;

public class SimpleIfDemo {
  public static void main(String[] args) {
    Scanner input = new Scanner(System.in);
    System.out.println("Enter an integer: ");
    int number = input.nextInt();

    if (number % 5 == 0)
      System.out.println("HiFive");

    if (number % 2 == 0)
      System.out.println("HiEven");
  }
}

SubtractionQuiz.java

import java.util.Scanner; 

public class SubtractionQuiz {
  public static void main(String[] args) {
    // 1. Generate two random single-digit integers
    int number1 = (int)(Math.random() * 10);
    int number2 = (int)(Math.random() * 10);

    // 2. If number1 < number2, swap number1 with number2
    if (number1 < number2) {
      int temp = number1;
      number1 = number2;
      number2 = temp;
    }

    // 3. Prompt the student to answer �what is number1 � number2?�
    System.out.print
      ("What is " + number1 + " - " + number2 + "? ");
    Scanner input = new Scanner(System.in);
    int answer = input.nextInt();

    // 4. Grade the answer and display the result
    if (number1 - number2 == answer)
      System.out.println("You are correct!");
    else {
      System.out.println("Your answer is wrong.");
      System.out.println(number1 + " - " + number2 + 
        " should be " + (number1 - number2)); 
    }
  }
}

TestBooleanOperators.java

import java.util.Scanner; 

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

    // Receive an input
    System.out.print("Enter an integer: ");
    int number = input.nextInt();

    if (number % 2 == 0 && number % 3 == 0)
      System.out.println(number + " is divisible by 2 and 3.");

    if (number % 2 == 0 || number % 3 == 0)
      System.out.println(number + " is divisible by 2 or 3.");

    if (number % 2 == 0 ^ number % 3 == 0)
      System.out.println(number + 
        " divisible by 2 or 3, but not both.");
  }
}