Getting Started with Eclipse
a. Make sure you have completed and understood the reading on IDEs and Eclipse.
b. Start Eclipse by typing the following in a terminal window.
$ eclipse &
You may recall that the ampersand means that the program will
run in the background and you can continue using the terminal
window.
Alternately, you can start Eclipse by finding the appropriate
menu item in the menu, which
looks like a little creature over a blue X under Xfce4.
Exercise 1: Your First Program
a. Make a new project in Eclipse and call it HelloEclipse.
From the menu, select ,
and then .
b. Create a package in the class that will hold your class files.
Name your package introduction.
If you are not sure how to create a new package, use
>
> .
c. Create a class in the package called HelloJava. If you are
not sure how to create a new class, use
>
> .
d. Copy and paste this code into your class. Make sure that you use
a package that corresponds to the one you just created.
package introduction;
/**
* A simple introductory Java class.
*/
public class HelloJava {
/**
* Print a silly message.
*/
public static void main(String[] args) {
System.out.print("I am the 1337 h4x0r. Phear me!");
} // main(String[])
} // class HelloJava
e. Run the program and marvel at the words that appear in the console!
Exercise 2: Switching Packages
a. Create a new package named
edu.grinnell.csc207.username.intro.
(You should be using package names like this, so you might as well
get used to it.)
b. Drag HelloJava from one package to another in the
Package Explorer.
c. Observe what happens.
Exercise 3: Experiments with Output
You've already seen that Java looks a bit like C, except that it's also
a bit more verbose. For example, instead of printf with
a pattern, you use System.out.println. (In a few days,
you will stop using System.out and explore other ways to
do output.)
a. Determine what happens if you have multiple calls to
System.out.println.
b. Determine what happens if you use println with an
integer or real number rather than a string.
c. Determine what happens if you use System.out.print rather
than System.out.println.
d. Determine what happens when you try to print System.out.
That is, determine the result of
System.out.println(System.out);
Exercise 4: Your Second Program
a. Make another class in your package and call it SimpleMath
b. Using the skeleton from above write a program that computes and
prints out a simple sum. For example, your output might be
Adding 3 and 4 gives us 7.
Presumably, you wrote this program using a sequence of calls to
System.out.print and System.out.println. Can
we pack it into a single instruction?
c. Java “overloads” the + operation.
If you combine two strings with +, you will get a string.
For example, determine the result of the following instruction.
System.out.println("Hello" + "World");
d. We saw earlier that System.out.println accepts things other
than strings, such as integers and reals (and even System.out).
What about +? Determine what happens if you combine a string
and an integer with +. What about combining an integer
and a string?
e. Rewrite your instructions to print a sum using just one call to
System.out.println.
Exercise 5: Configuring Eclipse
In this course, we will be trying to follow the standard Sun (now
Oracle) Java Code Conventions. Eclipse can help if you configure it
correctly.
First, select > .
Next, select > > .
Next, select under
Active Profile.
Finally, save the new preferences.
Select all of your code and hit Ctrl-I
a. Hover the cursor over one of the instances of System
and note what happens.
b. Hover the cursor over one of the instances of out and
note what happens.
c. Hover the cursor over one of the instances of print or
println and observe what happens.
d. Hover the cursor over main or HelloJava and
observe what happens.
