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@rjlutz rjlutz/ComputeAngles.java
Last active Jun 19, 2017

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Math, Characters, Strings (Chapter 4) - examples from Liang Intro to Java Comprehensive 10e
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);
}
}
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));
}
}
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 + "!");
}
}
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");
}
}
}
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");
}
}
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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