JAVA Script Lecture 1

Goal

Learn enough Java to do something useful Examples:

• Simulate a natural/engineering process

• Manipulate PDFs

• Draw pretty graphics

The Computer

Memory

Central Processing Unit (CPU)

Input/Output (IO) Devices Memory

Programming Languages

• Easier to understand than CPU instructions

• Needs to be translated for the CPU to understand it

Java

• “Most popular” language

• Runs on a “virtual machine” (JVM)

• More complex than some (eg. Python)

• Simpler than others (eg. C++)

First Program

class Hello {

public static void main(String[] arguments) {

// Program execution begins here

System.out.println("Hello world.");

}

}

1.Program Structure

class CLASSNAME {

public static void main(String[] arguments) {

STATEMENTS

}

}

2. Output

   System.out.println(some String) outputs to the console

   Example:

   System.out.println(“output”);

3. Second Program

   class Hello2 {

   public static void main(String[] arguments) {

   System.out.println("Hello world."); // Print once

   System.out.println("Line number 2"); // Again!

   }

   }

4. Types

   Kinds of values that can be stored and manipulated.

   boolean: Truth value (true or false).

   int: Integer (0, 1, -47).

   double: Real number (3.14, 1.0, -2.1).

   String: Text (“hello”, “example”).

5. Variables

   Named location that stores a value of one particular type.

   Form: TYPE NAME;

   Example: String foo;

6. Operators

   Symbols that perform simple computations

   Assignment: =

   Addition: +

   Subtraction: -

   Multiplication: *

   Division: /

   1. Order of Operations Follows standard math rules:

      1. Parentheses

      2. Multiplication and division

      3. Addition and subtraction