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| <title> Debugging your programs </title> |
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| <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/qs-68.gif" width=452 height=198 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> </li> |
| <li> In the Package Explorer view, select the <em>junit.samples</em> package |
| and select the Run menu. Within the Run menu, select Debug As, and then Java |
| Application. 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 - junit.samples - /JUnit</em> item in the dialog, |
| then click <strong>OK</strong>. |
| <p> <img src="../images/qs-69.gif" width=297 height=451 alt="Type selection dialog"> </p> |
| </li> |
| <li> The program will run until the breakpoint is reached. When the breakpoint is hit, the Debug perspective opens, and execution |
| is suspended. Notice that the process is still active (not terminated) in |
| the Debug view. Other threads might still be running. |
| <p> <img src="../images/qs-70.gif" alt="Debug perspective" width="685" height="563"> </p> |
| <em>Note: The breakpoint now has a checkmark overlay since the class |
| VectorTest was loaded in the Java VM.</em> </li> |
| <li> In the editor in the Debug perspective, select the entire line where the |
| breakpoint is set, and from its context menu, select <strong>Inspect</strong>. |
| <p> <img src="../images/qs-71.gif" alt="VectorTest.java editor with selected breakpoint line showing context menu" width="632" height="450"> |
| </p> |
| </li> |
| <li> The expression is evaluated in the context of the current stack frame, |
| and the results are displayed in the Expressions view. |
| </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 fFull tree in the Variables view until you can see |
| elementCount. |
| <p> <img src="../images/qs-72.gif" alt="Variables view" width="445" height="237"> </p> |
| </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> 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). |
| </li> |
| <li> Try some other step buttons (<strong>Step Into, 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>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><img border="0" src="../images/ngrelc.gif" alt="Related concepts" width="159" height="27"><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.gif" alt="Related tasks" width="159" height="27"><br> |
| <a href="../tasks/tasks-144.htm">Adding breakpoints</a><br> |
| <a href="../tasks/tasks-135.htm">Resuming the execution of suspended threads</a><br> |
| <a href="../tasks/tasks-126.htm">Running and debugging</a><br> |
| <a href="../tasks/tasks-134.htm">Suspending threads</a></p> |
| |
| <p><img src="../images/ngrelr.gif" width=159 height=27 border="0" alt="Related reference"><br> |
| <a href="../reference/ref-11.htm">Debug preferences</a><br> |
| <a href="../reference/ref-51.htm">Debug view</a><br> |
| <a href="../reference/ref-4.htm">Run and debug actions</a><br> |
| <a href="../reference/ref-35.htm">Breakpoints view</a><br> |
| <a href="../reference/ref-45.htm">Console view</a><br> |
| <a href="../reference/ref-52.htm">Display view</a><br> |
| <a href="../reference/ref-56.htm">Expressions view</a><br> |
| <a href="../reference/ref-74.htm">Variables view</a></p> |
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| <p> <a href="../hglegal2003.htm"><img src="../images/ngibmcpy2003.gif" alt="Copyright (c) 2000, 2003 IBM Corporation and others. All Rights Reserved." border="0" height="14" width="324"></a> |
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