Week 1 Becoming Familiar with Your Computer

CS 1063 Week 1: Introduction to Computer Programming

Objectives

Administrative
Use the web to obtain class notes, assignments, projects, and calendar dates
Type in a simple program in JBuilder and execute it

Reading Week 1

Administrative

Syllabus
Fill out survey
Binder and floppy disk
Borland JBuilder software
Course mechanics

Labs (12)
Quizzes (10)
Projects (3)
Tests (2 and a final)

Course web page

http:/www.cs.utsa.edu/~javalab

Activity 1: Compiling a Simple Program

Complete instructions for JBuilder can be found at http://www.cs.utsa.edu/~javalab/lab/gettingStartedJbuilder.html

Part 1: Setup - Find JBuilder on your computer and execute it.

Project/Package Name: helloworldpkg
Add a new Main Class with name: HelloWorld.Remember to check the box Generate main method.
Save all
You will need to type in the highlighted line below replacing the one that is there.

Java is case-sensitive. You must enter upper and lowercase letters exactly as they appear in the program listing.

Right click on the HelloWorld tab and chose run using defaults. you should see Hello, World! in the output window.

public class HelloWorld {

    public HelloWorld() {
    }

    public static void main(String[] args) {
        System.out.println("Hello World");
    }

}

Part 2: Construction

Every Java application contains a class with a main method. When the application starts, the instructions in the main method are executed.

public static void main(String[] args) { . . .}

Use comments to help human readers understand your program. Add the following line to your program. run

    public class HelloWorld {

    public HelloWorld() {
    }

    public static void main(String[] args) {         // display a greeting in the console window        System.out.println("Hello World");
    }

    }

Any text enclosed between // and the end of the line is completely ignored by the compiler.
Comments are used to explain the program to other programmers or to yourself.
The compiler also ignores any text between a /* and */ If you have a comment that is longer than one line then the /* . . . */ comment is simpler. For example

/* This is a simple Java program
It will print a greeting to the console
*/

Add the highlighted lines to your HelloWorld file and run again. Was there any change?

Instructions or statements in the body of the main method (statements between {} ) are executed one at a time. Each statement ends in a semicolon (;)

Notice that our main has only one statement - the System.out.println("Hello World");
The comment is ignored by the compiler

Whenever you call a method in Java, you need to specify three things

The object that you want to use - System.out
The name of the method you want to use - println
A pair of parentheses, containing any other information the method needs - ("Hello World")

Part 3: More on the System.out.println statement and strings. Add the highlighted lines to your HelloWorld file and run.

String - a sequence of characters enclosed in quotation marks.
The println method prints a string or a number and then starts a new line. The following code prints out the two lines

Hello

World!

System.out.println("Hello");
System.out.println("World!");

You can also print numerical values. The following code prints the number 7.

System.out.println(3 + 4);

The print method can be used to print an item without starting a new line afterward. The following code outputs the two statements in the single line

007

System.out.print("00");
System.out.println(3 + 4);

Add the highlighted statements in part 3 to your HelloWorld file and varify that your code works as intended.

Part 4: Escape Sequences Add the highlighted lines to your HelloWorld file and run

When printing some characters the compiler will report an error. Print out the sequence Hello, "World"! The following statement would generate such an error Why?.

System.out.println("Hello, "World"!");

If you precede the quotation marks inside the string with a backslash character (\") the " will be printed. The backslash character is used as an escape character, and the character sequence \" is called an escape sequence. The backslash does not denote itself; instead, it is used to encode other characters that would otherwise be difficult to include in a string. The correct way to do this is:

System.out.println("Hello, \"World\"!");

Another character that is difficult to print is the \ Print the following message: C:\courses\cs1063

System.out.println("C:\\courses\\cs1063");

The newline sequence is \n Each time it appears between quotes the output will go to the next line. Print the following characters.

                   *
                   **
                   ***

                   System.out.println("*\n**\n***\n");

The tab sequence is \t Each time it appears between quotes the output will space over before printing the next part of the string. Print the following characters.

               *        **        ***

                 System.out.println("*\t**\t***");

Add the highlighted statements in part 4 to your HelloWorld file and varify that your code works as intended.

Last Modified: August 21, 2005 at 2:51pm