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<html><head><meta http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>The Mandatory First Example</title><meta name="generator" content="DocBook XSL Stylesheets V1.73.2"><link rel="start" href="index.html" title="jEdit 4.3 User's Guide"><link rel="up" href="macro-basics.html" title="Chapter 13. Macro Basics"><link rel="prev" href="single-macros.html" title="Single Execution Macros"><link rel="next" href="predefined-variables.html" title="Predefined Variables in BeanShell"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">The Mandatory First Example</th></tr><tr><td width="20%" align="left"><a accesskey="p" href="single-macros.html">Prev</a> </td><th width="60%" align="center">Chapter 13. Macro Basics</th><td width="20%" align="right"> <a accesskey="n" href="predefined-variables.html">Next</a></td></tr></table><hr></div><div class="sect1" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="first-example"></a>The Mandatory First Example</h2></div></div></div><div class="informalexample"><pre class="programlisting">Macros.message(view, "Hello world!");</pre></div><p>Running this one line script causes jEdit to display a message box
        (more precisely, a <code class="classname">JOptionPane</code> object) with the
        traditional beginner's message and an <span class="guilabel"><strong>OK</strong></span> button.
        Let's see what is happening here.</p><p>This statement calls a static method (or function) named
        <code class="function">message</code> in jEdit's <a class="ulink" href="../api/org/gjt/sp/jedit/Macros.html" target="_top">Macros</a> class. If you
        don't know anything about classes or static methods or Java (or C++,
        which employs the same concept), you will need to gain some
        understanding of a few terms. Obviously this is not the place for
        academic precision, but if you are entirely new to object-oriented
        programming, here are a few skeleton ideas to help you with
        BeanShell.</p><div class="itemizedlist"><ul type="disc"><li><p>An <em class="glossterm">object</em> is a collection of data
                that can be initialized, accessed and manipulated in certain
                defined ways.</p></li><li><p>A <em class="glossterm">class</em> is a specification of what
                data an object contains and what methods can be used to work
                with the data. A Java application consists of one or more
                classes (in the case of jEdit ,over 600 classes) written by the
                programmer that defines the application's behavior. A BeanShell
                macro uses these classes, along with built-in classes that are
                supplied with the Java platform, to define its own
                behavior.</p></li><li><p>A <em class="glossterm">subclass</em> (or child class) is a
                class which uses (or &#8220;<span class="quote">inherits</span>&#8221;) the data and
                methods of its parent class along with additions or
                modifications that alter the subclass's behavior. Classes are
                typically organized in hierarchies of parent and child classes
                to organize program code, to define common behavior in shared
                parent class code, and to specify the types of similar behavior
                that child classes will perform in their own specific
                ways.</p></li><li><p>A <em class="glossterm">method</em> (or function) is a
                procedure that works with data in a particular object, other
                data (including other objects) supplied as
                <em class="glossterm">parameters</em>, or both. Methods typically
                are applied to a particular object which is an
                <em class="glossterm">instance</em> of the class to which the method
                belongs.</p></li><li><p>A <em class="glossterm">static method</em> differs from other
                methods in that it does not deal with the data in a particular
                object but is included within a class for the sake of
                convenience.</p></li></ul></div><p>Java has a rich set of classes defined as part of the Java
        platform. Like all Java applications, jEdit is organized as a set of
        classes that are themselves derived from the Java platform's classes. We
        will refer to <em class="firstterm">Java classes</em> and <em class="firstterm">jEdit
        classes</em> to make this distinction. Some of jEdit's classes
        (such as those dealing with regular expressions and XML) are derived
        from or make use of classes in other open-source Java packages. Except
        for BeanShell itself, we won't be discussing them in this guide.</p><p>In our one line script, the static method
        <code class="function">Macros.message()</code> has two parameters because that is
        the way the method is defined in the <a class="ulink" href="../api/org/gjt/sp/jedit/Macros.html" target="_top">Macros</a> class. You must
        specify both parameters when you call the function. The first parameter,
        <em class="parameter"><code>view</code></em>, is a variable naming the current, active
        <a class="ulink" href="../api/org/gjt/sp/jedit/View.html" target="_top">View</a> object.
        Information about pre-defined variables can be found in <a class="xref" href="predefined-variables.html" title="Predefined Variables in BeanShell">the section called &#8220;Predefined Variables in BeanShell&#8221;</a>.</p><p>The second parameter, which appears to be quoted text, is a
        <em class="glossterm">string literal</em> - a sequence of characters of
        fixed length and content. Behind the scenes, BeanShell and Java take
        this string literal and use it to create a <code class="classname">String</code>
        object. Normally, if you want to create an object in Java or BeanShell,
        you must construct the object using the <code class="function">new</code> keyword
        and a <em class="firstterm">constructor</em> method that is part of the
        object's class. We'll show an example of that later. However, both Java
        and BeanShell let you use a string literal anytime a method's parameter
        calls for a <code class="classname">String</code>.</p><p>If you are a Java programmer, you might wonder about a few things
        missing from this one line program. There is no class definition, for
        example. You can think of a BeanShell script as an implicit definition
        of a <code class="function">main()</code> method in an anonymous class. That is
        in fact how BeanShell is implemented; the class is derived from a
        BeanShell class called <a class="ulink" href="../api/bsh/XThis.html" target="_top">XThis</a>.
        If you don't find that helpful, just think of a script as one or more
        blocks of procedural statements conforming to Java syntax rules. You
        will also get along fine (for the most part) with C or C++ syntax if you
        leave out anything to do with pointers or memory management - Java and
        BeanShell do not have pointers and deal with memory management
        automatically.</p><p>Another missing item from a Java perspective is a
        <code class="function">package</code> statement. In Java, such a statement is
        used to bundle together a number of files so that their classes become
        visible to one another. Packages are not part of BeanShell, and you
        don't need to know anything about them to write BeanShell macros.</p><p>Finally, there are no <code class="function">import</code> statements in
        this script. In Java, an <code class="function">import</code> statement makes
        public classes from other packages visible within the file in which the
        statement occurs without having to specify a fully qualified class name.
        Without an import statement or a fully qualified name, Java cannot
        identify most classes using a single name as an identifier.</p><p>jEdit automatically imports a number of commonly-used packages
        into the namespace of every BeanShell script. Because of this, the
        script output of a recorded macro does not contain
        <code class="function">import</code> statements. For the same reason, most
        BeanShell scripts you write will not require <code class="function">import</code>
        statements.</p><p>Java requires <code class="literal">import</code> statement to be located at
        the beginning of a source file. BeanShell allows you to place
        <code class="literal">import</code> statements anywhere in a script, including
        inside a block of statements. The <code class="literal">import</code> statement
        will cover all names used following the statement in the enclosing
        block.</p><p>If you try to use a class that is not imported without its
        fully-qualified name, the BeanShell interpreter will complain with an
        error message relating to the offending line of code.</p><div class="sidebar"><p class="title"><b></b></p><p>Here is the full list of packages automatically imported by
            jEdit:</p><pre class="programlisting">java.awt
java.awt.event
java.net
java.util
java.io
java.lang
javax.swing
javax.swing.event
org.gjt.sp.jedit
org.gjt.sp.jedit.browser
org.gjt.sp.jedit.buffer
org.gjt.sp.jedit.gui
org.gjt.sp.jedit.help
org.gjt.sp.jedit.io
org.gjt.sp.jedit.msg
org.gjt.sp.jedit.options
org.gjt.sp.jedit.pluginmgr
org.gjt.sp.jedit.print
org.gjt.sp.jedit.search
org.gjt.sp.jedit.syntax
org.gjt.sp.jedit.textarea
org.gjt.sp.util</pre></div></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="single-macros.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="macro-basics.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="predefined-variables.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">Single Execution Macros </td><td width="20%" align="center"><a accesskey="h" href="index.html">Home</a></td><td width="40%" align="right" valign="top"> Predefined Variables in BeanShell</td></tr></table></div></body></html>