3: Using the Eclipse Workbench in Java

Generation QR Code in Java 3: Using the Eclipse Workbench

When you use a view to change something, the change takes place immediately For example, when you select Delete on the Package Explorer s context menu, whatever file you ve selected is deleted immediately In a way, this behavior is nothing new The same kind of thing happens when you delete a file using My Computer or Windows Explorer Editor: A part of the Eclipse workbench that displays information for you to modify A typical editor displays information in the form of text This text can be the contents of a file For example, an editor in the middle of Figure 3-1 displays the contents of the Playerjava source file Some editors display more than just text For instance, Figure 3-5 displays part of the Plug-in manifest editor Like many other editors, this manifest editor displays the contents of a file But instead of showing you all the words in the file, the manifest editor displays the file s contents as a form on a Web page

To find out what the Plug-in manifest editor is all about, see this book s Web site When you use an editor to change something, the change doesn t take place immediately For example, look at the editor in the middle of Figure 3-1 This editor displays the contents of the Playerjava source file You can type all kinds of things in the editor pane Nothing happens to Playerjava until you choose File Save from the Eclipse menu bar Of course, this behavior is nothing new The same kind of thing happens when you work in Microsoft Word or UNIX vi Like other authors, I occasionally become lazy and use the word view when I really mean view or editor When you catch me doing this, just shake your head and move onward When I m being very careful, I use the official Eclipse terminology I refer to views and editors as parts of the Eclipse workbench Unfortunately, this parts terminology doesn t stick in peoples minds very well Tab: Something that s impossible to describe except by calling it a tab That which we call a tab by any other name would move us as well from one view to another or from one editor to another The important thing is, views can be stacked on top of one another Eclipse displays stacked views as if they re pages in a tabbed notebook That s why a bunch of stacked views is called a tab group To bring a view in the stack to the forefront, you click that view s tab And, by the way, all this stuff about tabs and views holds true for tabs and editors The only interesting thing is the way Eclipse uses the word editor In Eclipse, each tabbed page of the editor area is an individual editor For example, the editor area in Figure 3-6 contains three editors (not three tabs belonging to a single editor) Active view or active editor: In a tab group, the view or editor that s in front In Figure 3-6, the Playerjava editor is the active editor The Accountjava and UseAccountjava editors are inactive

You can right-click a file in the Package Explorer Then, when you select Delete, Eclipse asks for confirmation Are you sure you want to delete the file If you click Yes (you do want to delete the file), then Eclipse removes the file from your computer s hard drive Okay, you deleted the file Now what if you change your mind Can you get the file back Don t bother looking for the file in your system s Recycle Bin Eclipse doesn t use the Recycle Bin Instead, Eclipse copies the file in its own local history Eclipse s local history maintains copies of things that you modify or delete To restore a file that you deleted, do the following: 1 Right-click a package or project branch in the Package Explorer or the Navigator view 2 In the resulting context menu, select Restore from Local History The Restore from Local History dialog appears The dialog contains a list of deleted files, along with a check box for each file in the list 3 Put a check mark next to the file that you want to undelete 4 Click Restore Hooray! You have your file again With Eclipse s local history, you can roll back small changes that you make to your Java source code Here s an example: 1 Use the editor to modify some Java source code 2 Choose File Save 3 Right-click the source code in the editor In the resulting context menu, choose Replace With Local History The Replace from Local History dialog appears The dialog s list contains the dates and times of any changes that you saved 4 Select a date and time The dialog shows you the changes you ve made since the selected date and time 5 Click Replace Eclipse puts the file back the way it was on the selected date at the selected time You can decide how much stuff to save in Eclipse s local history Choose Window Preferences on Eclipse s menu bar In the Preferences dialog s navigation tree, expand the Workbench branch Then, in the Workbench branch, select Local History In response, Eclipse provides Days to Keep Files, Entries per File, and Maximum File Size text fields