| <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0//EN"> |
| <html> |
| <head> |
| <meta name="copyright" content="Copyright (c) IBM Corporation and others 2000, 2007. This page is made available under license. For full details see the LEGAL in the documentation book that contains this page." > |
| <meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"> |
| <meta http-equiv="Content-Style-Type" content="text/css"> |
| <link rel="stylesheet" href="../book.css" charset="ISO-8859-1" type="text/css"> |
| <title> Debugging your programs </title> |
| </head> |
| <body> |
| <h1> Debugging your programs </h1> |
| <p> In this section, you will debug a Java program. </p> |
| <ol> |
| <li> In the Package Explorer view in the Java perspective, double-click <em>junit.samples.VectorTest.java</em> |
| to open it in an editor. </li> |
| <li> Place your cursor on the vertical ruler along the left edge of the editor |
| area on the following line in the setUp() method: |
| <p> <code>fFull.addElement (new Integer(1));</code> </p> |
| <p> and double-click on the ruler to set a breakpoint. </p> |
| <p> <img src="images/editor_vectortest_debug.png" alt="VectorTest.java editor showing added breakpoint"> |
| </p> |
| The breakpoint icon indicates the status of the breakpoint. The plain |
| blue breakpoint icon indicates that the breakpoint has been set, but not yet |
| installed. |
| <p> |
| <em>Note: Once the class is loaded by the Java VM, the breakpoint will be |
| installed and a checkmark overlay will be displayed on the breakpoint icon.</em> </p></li> |
| <li> In the Package Explorer view, select the <em>junit.samples</em> package |
| and select <strong>Debug As</strong>, and then <strong>Java |
| Application</strong>. When you run a program from a package, you will be |
| prompted to choose a type from all classes in the package that define a <code>main |
| </code>method. </li> |
| <li> Select the <em>VectorTest</em> item in the dialog, |
| then click <strong>OK</strong>. |
| <p> <img src="images/select_java_app_dialog.png" alt="Type selection dialog"> </p> |
| <p><em>Note: You can also simply hit the debug button <img src="images/debug_button.png" alt="Debug button"> |
| which will launch the currently selected resource or active editor. Select |
| <strong>Java Application </strong>when you are prompted to select a way |
| to debug VectorTest.</em></p> |
| <p><img src="images/select_how.png" alt="Select way to debug VectorTest"></p> |
| </li> |
| <li> The program will run until the breakpoint is reached. When the breakpoint is hit, execution |
| is suspended, and you are asked whether to open the Debug perspective. Click <strong>Yes</strong>. |
| Notice that the process is still active (not terminated) in |
| the Debug view. Other threads might still be running. |
| <p> <img src="images/workbench_debug_vectortest.png" alt="Debug perspective"> </p> |
| <em>Note: The breakpoint now has a checkmark overlay <img src="images/active_break_point.png" alt="Breakpoint with overlay"> since the class |
| VectorTest was loaded in the Java VM.</em> </li> |
| <li> In the editor in the Debug perspective, select <code>new Vector()</code> from the line above |
| where the breakpoint is set, and from its context menu, select <strong>Inspect</strong>. |
| <p> <img src="images/editor_vectortest_inspect.png" alt="VectorTest.java editor with selected breakpoint line showing context menu"> |
| </p> |
| </li> |
| <li> The expression is evaluated in the context of the current stack frame, |
| and a pop-up appears which displays the results. You can send a result to |
| the Expressions view by pressing the key binding displayed in the pop-up. |
| </li> |
| <li> Expressions that you evaluate while debugging a program will be listed in |
| this view. To delete an expression after working with it, select the |
| expression and choose <strong>Remove</strong> from its context menu. |
| </li> |
| <li> The Variables view (available on a tab along with the Expressions view) displays the values of the variables in the selected |
| stack frame. Expand the this.fFull tree in the Variables view until you can see |
| elementCount. |
| </li> |
| <li> The variables (e.g., elementCount) in the Variables view will change when |
| you step |
| through VectorTest in the Debug view. To step through the code, click the |
| <strong>Step Over</strong> (<img src="../images/org.eclipse.debug.ui/elcl16/stepover_co.png" alt="Step Over" >) button. |
| Execution will continue at the next line in the same method |
| (or, if you are at the end of a method, it will continue in the method from |
| which the current method was called). |
| <p> <img src="images/view_variables_1.png" alt="Variables view"> </p> |
| </li> |
| <li>In the variables view you can choose to see certain types as logical structures. This hides the implementation details of a |
| type and simply shows it as arrays or fields. You can define logical structures by yourself in the preference page <strong>Java > Debug > Logical Structures</strong>. |
| <p> <img src="images/view_variables_logical_structures.png" alt="fFull shown as logical structure"> </p> |
| </li> |
| <li> Try some other step buttons |
| (<strong>Step Into <img src="../images/org.eclipse.debug.ui/elcl16/stepinto_co.png" alt="Step Into" >, |
| Step Return <img src="../images/org.eclipse.debug.ui/elcl16/stepreturn_co.png" alt="Step Return" >) </strong>to |
| step through the code. Note the differences in stepping techniques. |
| </li> |
| <li> You can end a debugging session by allowing the program to run to |
| completion or by terminating it. |
| <ul> |
| <li>You can continue to step over the code with the <strong>Step </strong>buttons |
| until the program completes.</li> |
| <li>You can click the <strong>Resume </strong> |
| (<img src="../images/org.eclipse.debug.ui/elcl16/resume_co.png" alt="Resume" >) button to allow the |
| program to run until the next breakpoint is encountered or until the |
| program is completed.</li> |
| <li>You can select |
| <strong>Terminate</strong> from the context menu of the program's |
| process in the Debug view to terminate the program.</li> |
| </ul> |
| </li> |
| </ol> |
| <P class="nav_footer" id="nav_footer">Next Section: <A href="qs-14.htm">Evaluating expressions</A> |
| </P> |
| <p><img border="0" src="../images/ngrelc.png" alt="Related concepts" ><br> |
| <a href="../concepts/cbrkpnts.htm">Breakpoints</a><br> |
| <a href="../concepts/cremdbug.htm">Remote debugging</a><br> |
| <a href="../concepts/clocdbug.htm">Local debugging</a></p> |
| |
| <p><img border="0" src="../images/ngrelt.png" alt="Related tasks" ><br> |
| <a href="../tasks/task-add_line_breakpoints.htm">Adding breakpoints</a><br> |
| <a href="../tasks/task-resuming_threads.htm">Resuming the execution of suspended threads</a><br> |
| <a href="../tasks/task-running_and_debugging.htm">Running and debugging</a><br> |
| <a href="../tasks/task-suspending_threads.htm">Suspending threads</a></p> |
| |
| <p><img src="../images/ngrelr.png" border="0" alt="Related reference"><br> |
| <a href="../reference/preferences/java/debug/ref-debug.htm">Debug preferences</a><br> |
| <a href="../reference/views/debug/ref-debug_view.htm">Debug view</a><br> |
| <a href="../reference/menus/run/ref-menu-run.htm">Run menu actions</a><br> |
| <a href="../reference/ref-toolbar-run.htm">Run and debug toolbar actions</a><br> |
| <a href="../reference/views/breakpoints/ref-breakpoints_view.htm">Breakpoints view</a><br> |
| <a href="../reference/views/console/ref-console_view.htm">Console view</a><br> |
| <a href="../reference/views/display/ref-display_view.htm">Display view</a><br> |
| <a href="../reference/views/expressions/ref-expressions_view.htm">Expressions view</a><br> |
| <a href="../reference/views/variables/ref-variables_view.htm">Variables view</a></p> |
| |
| |
| </body> |
| </html> |
| |
