Java Programming Introduction

Study Notes

Java Programming Introduction

Java is a programming language used to create applications.
The Scanner class is used for accepting input from the user.
The import java.util.Scanner; line imports the necessary class.
A Scanner object is created using Scanner input = new Scanner(System.in);
System.in refers to the keyboard input.

Scanner Methods

nextInt(): Reads an integer from the user.
nextDouble(): Reads a double-precision floating-point number from the user.
nextFloat(): Reads a single-precision floating-point number from the user.
next(): Reads a string from the user, up to the next whitespace.
next().charAt(0): Reads a character from the user input.
Each method waits for the user to press Enter.

Example Usage (Scanner)

Get user input for age:

System.out.print("How old are you? ");
int age = input.nextInt();
System.out.println("You typed " + age);

Java Math Class

Provides mathematical functions.
Math.abs(value): Returns the absolute value of a number.
Math.ceil(value): Rounds a number up to the nearest integer.
Math.floor(value): Rounds a number down to the nearest integer.
Math.log10(value): Returns the base-10 logarithm of a number.
Math.max(value1, value2): Returns the larger of two values.
Math.min(value1, value2): Returns the smaller of two values.
Math.pow(base, exp): Returns base raised to the power of exp.
Math.random(): Returns a random double between 0.0 (inclusive) and 1.0 (exclusive).
Math.round(value): Rounds a number to the nearest integer.
Math.sqrt(value): Returns the square root of a number.
Math.sin(value), Math.cos(value), Math.tan(value): Trigonometric functions (value in radians).
Math.toDegrees(value), Math.toRadians(value): Converts between degrees and radians.
- Math.E: Euler's number (approximately 2.71828).
- Math.PI: Pi (approximately 3.14159).
Math methods do not print directly to the console.
The result is a numerical value

Type Casting

Converts a variable from one data type to another.
(type) expression: Explicit type casting.
Example: (double) 19 / 5 converts the result of the division to a double-precision number.
(int) Math.pow(10, 3) truncates Math.pow's results to an integer.

Calling Math Methods

Parameters provide input; return values give outputs from the method.

Example: Hypotenuse Calculation

Calculate the hypotenuse of a right-angled triangle using user input for the sides

import java.util.Scanner; // Import necessary class
public class Main {
    public static void main(String[] args) {
	Scanner input = new Scanner(System.in); //Create an object from Scanner class
		//Get the inputs from user
		System.out.print("Please Enter the value of side 1");
		double side1 = input.nextDouble();
		System.out.print("Please Enter the value of side 2");
		double side2 = input.nextDouble();
		//Calculate hypotenuse
		double hypotenuse = Math.sqrt((side1 * side1) + (side2 * side2));
		//Display output to user
	System.out.println("The length of the hypotenuse is :"+hypotenuse);
	}
}