Exercise : Compile and run a program in jGRASP

Recall from lecture: A Java program must be compiled, or translated into binary instructions. Then it can be executed or run. When you run a program, it displays output messages to the user in a text window called a console.

For this exercise, let's compile and run a short program that we will provide to you. (See the following slides.) If you get stuck, ask a classmate or TA for help.

Exercise - run jGRASP and create file

• Run the jGRASP editor from the Start Menu of the lab computer (or run it from your own laptop, if you brought one).
• In jGRASP, create a new Java program: Click File → New → Java from the top menu. An empty white text window should appear in jGRASP.
  

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Exercise - copy/paste

• Copy and paste the following program into jGRASP:

  public class MyFirstProgram {
      public static void main(String[] args) {
          System.out.println("Hello, world!");
          System.out.println();
          System.out.println("This is my very first program.");
          System.out.println("Hooray!");
      }
  }
  

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Exercise - save

• Save the program: Click the Save toolbar button, or click File → Save from the top menu, or press the hotkey Ctrl-S (Command-S on a Mac).
• The file name must end with .java and must match the 'public class' name from the Java program. Name this file MyFirstProgram.java.

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Exercise - compile

• Compile the program (translate it to binary instructions): Press the toolbar button that looks like a green plus (+) sign. Or press hotkey Ctrl-B. You should see "jGRASP: operation complete".
  

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Exercise - run

• Run the program: Press the toolbar button that looks like a running man. Or press hotkey Ctrl-R. You should see the program's output in the bottom console area.