1. Your First Java Program: HelloWorld.java
Computer Programming
Your First Java Program: HelloWorld.java
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Trade & Industrial Education

2. HelloWorld.java // Name: your name here // Date: today’s date here
// Program: HelloWorld.java
public class HelloWorld {
public static void main (String[] args)
System.out.println ("Hello World!"); }
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IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education

3. Comments // Name: your name here // Date: today’s date here
// Program: Hello World
Lines 1-3 are comments.
Comments begin with //
Comments are ignored by the compiler
Used to give information to the reader
Copyright © Texas Education Agency, 2013
IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education

4. Program Declaration public class HelloWorld
Line 4 is the program declaration.
“public” is a key word indicating that the class file is usable by the public.
“class” indicates that the file is a program. Classes are the building blocks of Java.
“HelloWorld” is the name of the file. Java is case-sensitive. The file must be saved as “HelloWorld.java”.
Copyright © Texas Education Agency, 2013
IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education

5. Braces { Line 5 begins the program with an opening curly brace({)
Braces enclose statements that make up a programming block.
Each opening brace must have a matching closing brace.
Copyright © Texas Education Agency, 2013
IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education

6. The main method public static void main (String[] args)
Line 6 is the main method declaration.
A method contains programming statements.
Every Java application must have a “main” method.
(String[] args) is the parameter for the main method.
Parameters will be discussed in detail later.
Copyright © Texas Education Agency, 2013
IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education

7. Braces { Line 7 begins the main method with an opening curly brace({).
Braces enclose statements that make up a programming block.
Each opening brace must have a matching closing brace.
Copyright © Texas Education Agency, 2013
IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education

8. The main method System.out.println ("Hello World!");
Line 8 prints a line of text.
The text that will be printed is enclosed in parentheses.
The statement ends with a semicolon.
“Hello World” is the text that will be displayed.
Text enclosed in quotes is called a string.
Copyright © Texas Education Agency, 2013
IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education

9. Closing Braces }
Line 9 and 10 close the braces that were opened on lines 5 and 7.
Indenting is not necessary but helps to make the program more readable.
Copyright © Texas Education Agency, 2013
IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education

10. Running the Program
When you run the program, Hello World! Should display in the output window.
Copyright © Texas Education Agency, 2013
IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education

11. Introducing Errors
Programmers are always fixing errors. We will explore a few types of errors: Line 6: public static void main (String[] args) Change it to: public static vod main (String[] args) Compile and you will see the error: “cannot find symbol class vod” – therefore you need to correct the spelling. This is a compile-time error.
Copyright © Texas Education Agency, 2013
IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education

12. Ending the Lesson
Play around making changes and noting the errors. Do not introduce more than one error at a time!
Copyright © Texas Education Agency, 2013
IT: Beginning Computer Programming- First Java Program
Trade & Industrial Education