Lab 1 – The First Cup of Java

Lab 1 – The First Cup of Java

• Lab 1 Home
• Warmup
• Part 1
• Part 2
• Part 3
• Submission

Part 1 – Pyramids revisited

Create a new folder for your project called Lab1. Create the Java project in Eclipse by selecting “File” > “New” > “Java Project”. Give it the project name Lab 1. Uncheck the Use default location box. After you uncheck this box, the Location textbox becomes active. Use the browse button to select the Lab1 folder you created at the start. Click Finish.

Highlight Lab1, then select New from the File menu and Class from the popup list. This brings up the New Class window, which should already have Lab1/src as the source folder. If this is not the case use the Browse button to navigate to this folder. Next, it asks for a package name. Use lab1 for this. Use Pyramid as the name of the class and check the button for including a public static void main stub. Click the Finish button at the bottom and you are ready to start coding.

For your first program I want you to create a class called Pyramid that draws a simple pyramid out of * characters. Your program will:

• Check that the user has entered exactly 1 command line argument. To do this, use the String array parameter to main called args, and check that args.length is equal to 1. If it isn’t, you should print a message to the user and then quit by calling System.exit(1);

• Convert the command line argument to an integer. Integer.parseInt is a static method in the Integer class that allows you to convert a String that represents a number and turn it into an int. Use Integer.parseInt to convert the first argument args[0] into an int that represents the number of rows in your pyramid.

  int height = Integer.parseInt(args[0]);
  

• Print out the pyramid

Here are some examples of inputs and outputs. (Recall from the warmup that the way you provide command line arguments is from the Run > Run Configurations… menu option and then click on the (x)= Arguments tab.)

input: 5
output:
    *
   ***
  *****
 *******
*********

input: 1
output:
*

No input
output: 
You need to provide an argument!

You may want to spend a couple of minutes figuring out how many stars and how many spaces you will print in each line as a function of height and your loop index.

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