76 lines
4.6 KiB
HTML
76 lines
4.6 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html lang="en-us" xml:lang="en-us">
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<meta name="DC.Type" content="task" />
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<meta name="DC.Title" content="Evaluate variables in Java programs" />
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<meta name="abstract" content="There are two ways to evaluate a variable when a program stops running at a breakpoint or step." />
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<meta name="description" content="There are two ways to evaluate a variable when a program stops running at a breakpoint or step." />
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<meta name="copyright" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2006" />
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<meta name="DC.Identifier" content="evalvar" />
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Evaluate variables in Java programs</title>
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</head>
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<body id="evalvar"><a name="evalvar"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">Evaluate variables in Java programs</h1>
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<div><p>There are two ways to evaluate a variable when a program stops
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running at a breakpoint or step.</p>
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<div class="section"><ul><li>Option 1: Enter <samp class="codeph">EVAL VariableName</samp> on the debug command
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line.</li>
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<li>Option 2: Put the cursor on the variable name in the displayed source
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code and press F11 (Display variable).</li>
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</ul>
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<p>Use the EVAL command for evaluating variables in a Java™ program.</p>
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<div class="note"><span class="notetitle">Note:</span> You
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can also change the contents of a variable by using the EVAL command. For
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more information about the variations of the EVAL command, see <a href="../books/sc092712.pdf" target="_blank">WebSphere<sup>®</sup> Development Studio: ILE
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C/C++ Programmer's Guide, SC09-2712</a> and online help information.</div>
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<p>When
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looking at variables in a Java program, note the following:</p>
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<ul><li>If you evaluate a variable that is an instance of a Java class,
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the first line of the display shows what kind of object it is. It also shows
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an identifier for the object. Following the first display line, the contents
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of each field in the object displays. If the variable is null, the first line
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of the display indicates that it is null. Asterisks show the contents of each
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field (of a null object).</li>
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<li>If you evaluate a variable that is a Java string object, the contents of that
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string displays. If the string is null, then null displays.</li>
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<li>You cannot change a variable that is a string.</li>
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<li>If you evaluate a variable that is an array, 'ARR' displays followed by
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an identifier for that array. You can evaluate elements of the array by using
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a subscript of the variable name. If the array is null, then null displays.</li>
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<li>You cannot change a variable that is an array. You can change an element
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of an array if it is not an array of strings or objects.</li>
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<li>For variables that are arrays, you can specify arrayname.length to see
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how many elements are in the array.</li>
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<li>If you want to see the contents of a variable that is a field of a class,
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you can specify classvariable.fieldname.</li>
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<li>If you try to evaluate a variable before it has been initialized, one
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of two things can happen. Either a <samp class="codeph">Variable not available to display</samp> message
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is shown, or the uninitialized contents of the variable are shown, which could
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be a strange value.</li>
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</ul>
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</div>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="stepping.htm" title="You can step through your program while debugging. You can either step over or step into other functions. Java programs and native methods can use the step function.">Step through Java programs to debug</a></div>
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</div>
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</div>
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</body>
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</html>
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