Part I: Getting Started in Java

Generation Code 39 Extended in Java Part I: Getting Started

In this book I refer to the window in Figure 2-8 (the menu bar, the toolbar, the File View, General Output pane, and so on) as the JCreator work area But JCreator s help files use slightly different terminology In JCreator s help files, the window in Figure 2-8 is called the workspace, not the work area Elsewhere in these help files, JCreator reuses the word workspace to mean something entirely different To avoid any confusion, I use two different terms I use work area for the window in Figure 2-8, and I use workspace for that other, entirely different thing (I explain that entirely different thing in the next paragraph) JCreator divides Java programs into workspaces Each workspace is further subdivided into projects To organize this book s examples, I made a workspace for each chapter, and then made a project for each complete Java program When you open 02jcw, you get my 02 workspace a workspace that contains three projects The projects names are Program0201, Program0202, and Program0203 That s why, in JCreator s File View pane, you see a 02 tree with branches labeled Program0201, Program0202, and Program0203 (See Figure 2-8) Clicking Open in Step 4 may coax out a message box asking if you want to Save the workspace modifications If so, click Yes Clicking Open may coax out another box asking if you want to close all document Windows If so, click Yes

5 In the File View s tree, right-click the branch labeled Program0201 In the resulting context menu, choose Sets As Active Project (See Figure 2-9)

Choosing Sets As Active Project makes Program0201 the active project In JCreator, only one project at a time can be the active project To run a particular program, the program s code has to be in whatever project is currently active In JCreator s File View, you can tell which project is active by looking for the project whose name is displayed in boldface On some systems, the active project s name is a hazy, light-gray boldface If a particular program isn t in the active project, you can t run that program, but you can do some other things with that program For instance, you can see the program in one of JCreator s panes, make changes to the program, save the program, and so on For this reason, it s really easy to get confused and forget which project is active So always keep the active project in the forefront of your mind If your code doesn t do what you think it should do, check to make sure that the project you want to run is the active project 6 Choose Build Compile Project from the main menu Choosing Compile Project does exactly what it says It compiles the project s code (To find out what compile means, see the sidebar entitled Compiling and running a Java program ) After some pleasant chirping sounds from your hard drive, JCreator s bottom pane displays a Process completed message (See Figure 2-10) 7 Choose Build Execute Project from the main menu When you choose Execute Project, the computer runs the project s code (That is, the computer runs a Java program that I wrote) As part of the run, the message How much are you borrowing appears in JCreator s General Output pane (Refer to Figure 2-7)

8 Click anywhere inside JCreator s General Output pane, and then type a number, like 10000000, and press Enter When you type a number in Step 8, don t include your country s currency symbol and don t use a grouping separator (US residents, don t type a dollar sign and don t use commas) Things like $10000000 or 100,00000 cause the program to crash You see a NumberFormatException message in the General Output pane After you press Enter, the Java program displays another message (What s the interest rate ) in JCreator s General Output pane 9 In response to the interest rate question, type a number, like 525, and press Enter After you press Enter, the Java program displays another message (How many years ) in JCreator s General Output pane 10 Type a number, like 30, and press Enter In response to the numbers that you ve typed, the Java program displays a monthly payment amount Again, refer to Figure 2-7 (Disclaimer: Your local mortgage company will charge you much more than the amount that my Java program calculates) When you type a number in Step 10, don t include a decimal point Things like 300 cause the program to crash You see a NumberFormatException message in the General Output pane Occasionally you decide in the middle of a program s run that you ve made a mistake of some kind You want to stop the program s run dead in its tracks To do this, choose Tools Stop Tool from the main menu