Java Programming 1 Lecture PDF

Programming 1 Lecture 5 Chapter 2: Introduction to Java Programming Dr/ Mahmoud Gamal 1 Accepting Input from the User (Scanner): To call Scanner: import java.util.Scanner; Java.util ……>> Package Scanner……>> Class T...

Programming 1 Lecture 5 Chapter 2: Introduction to Java Programming Dr/ Mahmoud Gamal 1 Accepting Input from the User (Scanner): To call Scanner: import java.util.Scanner; Java.util ……>> Package Scanner……>> Class To create object (Data + Methods) from class scanner: Scanner Name = new Scanner (System.in) System.in …..>> refer to accepting input from keyboard Example: Scanner input = new Scanner (System.in) 2 Scanner methods Method Description nextInt() reads an int from the user nextDouble() reads a double from the user nextFloat() reads a float from the user next() reads a one-word String from the user next().charAt(0) reads one char from the user Each method waits until the user presses Enter. The value typed by the user is returned. Example: System.out.print("How old are you? "); int age = input.nextInt(); System.out.println("You typed " + age); Scanner Example import java.util.Scanner; // so that I can use Scanner public class UserInputExample { public static void main(String[] args) { Scanner console = new Scanner(System.in); System.out.print("How old are you? "); int age = console.nextInt(); age 29 years 36 int years = 65 - age; System.out.println(years + " years to retirement!"); } } Console (user input underlined): How old are you? 29 36 years until retirement! Example: A program to calculate the sum of two numbers Output: 5 Example: A Program to calculate the area of rectangle. Output: 6 Example: A Program to calculate the net salary 7 Java's Math class Method name Description Math.abs(value) absolute value Math.ceil(value) rounds up Math.floor(value) rounds down Math.log10(value) logarithm, base 10 Math.max(value1, value2) larger of two values Math.min(value1, value2) smaller of two values Math.pow(base, exp) base to the exp power Math.random() random double between 0 and 1 Math.round(value) nearest whole number Math.sqrt(value) square root Math.sin(value) sine/cosine/tangent of Math.cos(value) an angle in radians Constant Description Math.tan(value) Math.E 2.7182818... Math.toDegrees(value) convert degrees to Math.PI 3.1415926... Math.toRadians(value) radians and back Calling Math methods Math.methodName(parameters) Examples: double squareRoot = Math.sqrt(121.0); System.out.println(squareRoot); // 11.0 int absoluteValue = Math.abs(-50); System.out.println(absoluteValue); // 50 System.out.println(Math.min(3, 7) + 2); // 5 double exp = Math.pow(2, 4); System.out.println(exp); // 16.0 The Math methods do not print to the console. Each method produces ("returns") a numeric result. The results are used as expressions (printed, stored, etc.). Example: 10  Remember: Type casting type cast: A conversion from one type to another. To promote an int into a double to get exact division from / To truncate a double from a real number to an integer Syntax: (type) expression Examples: double result = (double) 19 / 5; // 3.8 int result2 = (int) result; // 3 int x = (int) Math.pow(10, 3); // 1000 Calling Math methods Parameters send information in from the caller to the method. Return values send information out from a method to its caller. A call to the method can be used as part of an expression. -42 Math.abs(-42) 42 main 2.71 3 Math.round(2.71) Example: Java program to find the Hypotenuse of a right-angled triangle 13