This document provides an introduction to the 6.092: Introduction to Java course. It covers the following key points in 3 or fewer sentences: The course aims to teach enough Java to do something useful, such as simulating processes or drawing graphics. Assignments are due within 24 hours and must be submitted individually, with students required to submit solutions for 6 or 7 assignments to pass. The document then provides an overview of Java concepts like data types, variables, operators, and program structure.

1. 6.092: Introduction to Java
1: Types, Variables, Operators

2. Goal
Learn enough Java to do something
useful
Examples:
• Simulate a natural/engineering process
• Manipulate PDFs
• Draw pretty graphics

3. Assignments
• View and submit via Stellar
• Due at 3 PM the next day (24 hours)
• Collaborate with others
• Write your own code
• Must submit first assignment
Must submit a “reasonable” attempt for 6/7
assignments to pass

4. The Computer
Central
Processing Unit
(CPU)
Input/Output
(IO) Devices
Memory

5. CPU Instructions
z = x + y Read location x
Read location y
Add
Write to location z

6. Programming Languages
• Easier to understand than CPU
instructions
• Needs to be translated for the CPU to
understand it

7. Java
• “Most popular” language
• Runs on a “virtual machine” (JVM)
• More complex than some (eg. Python)
• Simpler than others (eg. C++)

8. Compiling Java
Source Code
(.java)
Byte Code
(.class)
javac java

9. First Program
class Hello {
public static void main(String[] arguments) {
// Program execution begins here
System.out.println("Hello world.");
}
}

10. Program Structure
class CLASSNAME {
public static void main(String[] arguments) {
STATEMENTS
}
}

11. Output
System.out.println(some String) outputs to
the console
Example:
System.out.println(“output”);

12. Second Program
class Hello2 {
public static void main(String[] arguments) {
System.out.println("Hello world."); // Print once
System.out.println("Line number 2"); // Again!
}
}

13. 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”).

14. Variables
Named location that stores a value of one
particular type.
Form:
TYPE NAME;
Example:
String foo;

15. Assignment
Use = to give variables a value.
Example:
String foo;
foo = “IAP 6.092”;

16. Assignment
Can be combined with a variable
declaration.
Example:
double badPi = 3.14;
boolean isJanuary = true;

17. class Hello3 {
public static void main(String[] arguments) {
String foo = "IAP 6.092";
System.out.println(foo);
foo = "Something else";
System.out.println(foo);
}
}

18. Operators
Symbols that perform simple computations
Assignment: =
Addition: +
Subtraction: -
Multiplication: *
Division: /

19. Order of Operations
Follows standard math rules:
1. Parentheses
2. Multiplication and division
3. Addition and subtraction

20. class DoMath {
public static void main(String[] arguments) {
double score = 1.0 + 2.0 * 3.0;
System.out.println(score);
score = score / 2.0;
System.out.println(score);
}
}

21. class DoMath2 {
public static void main(String[] arguments) {
double score = 1.0 + 2.0 * 3.0;
System.out.println(score);
double copy = score;
copy = copy / 2.0;
System.out.println(copy);
System.out.println(score);
}
}

22. String Concatenation (+)
String text = "hello" + " world";
text = text + " number " + 5;
// text = "hello world number 5"

23. Assignment: GravityCalculator
Compute the position of a falling object:
x(t) = 0.5 × at2 + vit + xi

24. MIT OpenCourseWare
http://ocw.mit.edu
6.092 Introduction to Programming in Java
January (IAP) 2010
For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.