| <!DOCTYPE html |
| PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "../xhtml1-strict.dtd"> |
| <html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en"> |
| <head> |
| <meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /> |
| <link rel="stylesheet" type="text/css" href="../css/ot.css" /> |
| <link rel="stylesheet" type="text/css" href="../css/otjld.css" /> |
| <title>OT/J Language Definition v1.3</title> |
| </head> |
| <body class="otdt"> |
| <div id="content"> |
| <table class="nav"> |
| <tr> |
| <td class="back"><a id="top"></a><a href="s1.4.html" rel="prev"><< §1.4 Name clashes</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"></td> |
| </tr> |
| </table> |
| <div class="breadcrumb"><a class="nav" href="s1.html" rel="section">§1 Teams and Roles</a></div> |
| <div class="sect depth2" id="s1.5"> |
| <h2 class="sect">§1.5 Team and role nesting<a class="img" href="s1.5.html" |
| title="PermaLink to §1.5 Team and role nesting"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h2> |
| <p>Multi-level nesting of classes is restricted only by the following rules. |
| |
| </p> |
| <h5 class="listing">Example code (Nesting):</h5> |
| <div class="listing example frame" id="l1.5"> |
| <table class="listing"> |
| <tr class="line odd"> |
| <td class="ln">1</td> |
| <td><pre><b>public</b> <b>team</b> <b>class</b> SuperOuter {</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">2</td> |
| <td><pre> <b>public</b> <em><b>team</b> <b>class</b> RoleAndTeam</em> {</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">3</td> |
| <td><pre> <b>protected</b> <b>class</b> InnerRole {</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">4</td> |
| <td><pre> Runnable foo() { <b>return</b> null; }</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">5</td> |
| <td><pre> }</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">6</td> |
| <td><pre> }</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">7</td> |
| <td><pre> <b>public</b> <em><b>team</b> <b>class</b> RoleAndTeamSub</em> <b>extends</b> <strong>RoleAndTeam</strong> {</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">8</td> |
| <td><pre> <b>protected</b> <b>class</b> InnerRole {</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">9</td> |
| <td><pre> Runnable foo() { <b>throw</b> <b>new</b> RuntimeException(); }</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">10</td> |
| <td><pre> }</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">11</td> |
| <td><pre> }</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">12</td> |
| <td><pre>}</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">13</td> |
| <td><pre><b>public</b> <b>team</b> <b>class</b> OuterTeam <b>extends</b> SuperOuter {</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">14</td> |
| <td><pre> <b>public</b> <em><b>team</b> <b>class</b> RoleAndTeam</em> {</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">15</td> |
| <td><pre> <b>protected</b> <b>class</b> InnerRole {</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">16</td> |
| <td><pre> Runnable foo() {</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">17</td> |
| <td><pre> <b>class</b> Local {};</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">18</td> |
| <td><pre> <b>return</b> <b>new</b> Runnable() { <span class="comment">// anonymous class definition</span></pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">19</td> |
| <td><pre> <b>public</b> <b>void</b> run() {}</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">20</td> |
| <td><pre> };</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">21</td> |
| <td><pre> }</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">22</td> |
| <td><pre> <span class="comment">// <span class="error">class IllegalMember {}</span></span></pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">23</td> |
| <td><pre> }</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">24</td> |
| <td><pre> }</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">25</td> |
| <td><pre> <b>public</b> <em><b>team</b> <b>class</b> RoleAndTeamSub</em> {</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">26</td> |
| <td><pre> <b>protected</b> <b>class</b> InnerRole {</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">27</td> |
| <td><pre> Runnable foo() {</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">28</td> |
| <td><pre> <em>RoleAndTeamSub.tsuper</em>.foo();</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">29</td> |
| <td><pre> <b>return</b> <em>OuterTeam.tsuper</em>.foo();</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">30</td> |
| <td><pre> };</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">31</td> |
| <td><pre> }</pre></td> |
| </tr> |
| <tr class="line even"> |
| <td class="ln">32</td> |
| <td><pre> }</pre></td> |
| </tr> |
| <tr class="line odd"> |
| <td class="ln">33</td> |
| <td><pre>}</pre></td> |
| </tr> |
| </table> |
| </div> |
| <div class="subsect depth3" id="s1.5.a"> |
| <h4 class="subsect">(a) <span class="title">Nested teams</span><a class="img" href="s1.5.a.html" title="PermaLink to (a) Nested teams"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>If a role class is also marked using the <code>team</code> modifier, |
| it may contain roles at the next level of nesting. |
| |
| </p> |
| <div class="codecomment"> |
| <ul> |
| <li>In the above example (<a href="#l1.5" class="listing">Listing 1.5</a>) class <code>RoleAndTeam</code> starting in line 14 |
| is a role of <code>OuterTeam</code> and at the same time a |
| team containing a further role <code>InnerRole</code></li> |
| </ul> |
| </div> |
| <p>Such a hybrid role-and-team has all properties of both kinds of classes. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s1.5.b"> |
| <h4 class="subsect">(b) <span class="title">Nested classes of roles</span><a class="img" href="s1.5.b.html" |
| title="PermaLink to (b) Nested classes of roles"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>A regular role class (ie., not marked as <code>team</code>, see above) |
| may contain local types (see <a href="http://java.sun.com/docs/books/jls/second_edition/html/statements.doc.html#247766" |
| class="ext">JLS §14.3</a> |
| - in the example: class <code>Local</code>), anonymous types |
| (<a href="http://java.sun.com/docs/books/jls/second_edition/html/expressions.doc.html#252986" |
| class="ext">JLS §15.9.5</a> |
| - in the example: class defined in lines 18-20) |
| but no member types (<a href="http://java.sun.com/docs/books/jls/second_edition/html/classes.doc.html#246026" |
| class="ext">JLS §8.5</a> |
| - in the example: illegal class |
| <code>IllegalMember</code>). |
| <br /> |
| The effect is, that nested types of a regular role cannot be |
| used outside the scope of their enclosing role. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s1.5.c"> |
| <h4 class="subsect">(c) <span class="title">Prohibition of cycles</span><a class="img" href="s1.5.c.html" |
| title="PermaLink to (c) Prohibition of cycles"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>A nested team may not extend its own enclosing team. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s1.5.d"> |
| <h4 class="subsect">(d) <span class="title">Prohibition of name clashes</span><a class="img" href="s1.5.d.html" |
| title="PermaLink to (d) Prohibition of name clashes"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>A nested team may inherit roles from multiple sources: its explicit super team |
| and any of its implicit super classes (roles) from different levels of nesting. |
| If from different sources a team inherits two or more roles of the same name |
| that are not related by implicit inheritance, this is an illegal name clash. |
| |
| </p> |
| </div> |
| <div class="subsect depth3" id="s1.5.e"> |
| <h4 class="subsect">(e) <span class="title">Precedence among different supers</span><a class="img" href="s1.5.e.html" |
| title="PermaLink to (e) Precedence among different supers"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>If a role inherits the same feature from several super roles (super and tsuper), |
| an implicitly inherited version always overrides any explicitly inherited feature, |
| i.e., a role with the same simple name is closer related than one with a different name. |
| </p> |
| <p> |
| Also implicit inheritance alone may produce several candidate methods inherited by a role class. |
| This is a result of team-nesting where each level of nesting may add one more tsuper role |
| if outer teams also participate in an inheritance relationship. |
| In this case a role inherited from an <em>implicit</em> super team of the enclosing team |
| is closer related than a role inherited from an <em>explicit</em> super team. |
| If necessary this rule is applied inside out until a nesting level is found where indeed |
| explicit team inheritance is involved.<br /> |
| So when comparing classes by their fully qualified names |
| the longest common suffix will determine the closest relationship. |
| E.g., <code>SuperOuter.RoleAndTeamSub.InnerRole</code> |
| is the closest ancestor of <code>SubOuter.RoleAndTeamSub.InnerRole</code> |
| because both share the name suffix <code>RoleAndTeamSub.InnerRole</code>. |
| |
| </p> |
| <div class="codecomment"> |
| <table> |
| <colgroup span="1"> |
| <col align="left" span="1" /> |
| <col align="center" span="1" /> |
| </colgroup> |
| <tr> |
| <td valign="top" rowspan="1" colspan="1"> |
| <p>In the above example (<a href="#l1.5" class="listing">Listing 1.5</a>) role <code class="small">OuterTeam.RoleAndTeamSub.InnerRole</code> |
| has two direct tsuper roles: |
| <code class="small">OuterTeam.RoleAndTeam.InnerRole</code> and <code class="small">SuperOuter.RoleAndTeamSub.InnerRole</code>. |
| Without the method <code>foo</code> defined in lines 27-30, the enclosing class <code class="small">OuterTeam.RoleAndTeamSub.InnerRole</code> |
| would inherit the method <code>foo</code> defined in <code>SuperOuter.RoleAndTeamSub.InnerRole</code> (line 9), |
| because the common name suffix <code>RoleAndTeamSub.InnerRole</code> |
| creates a stronger relationship making that class the closest ancestor. |
| </p> |
| </td> |
| <td rowspan="1" colspan="1"><img src="../images/team_nesting_hor.png" alt="Example diagram team nesting" /></td> |
| </tr> |
| </table> |
| </div> |
| </div> |
| <div class="subsect depth3" id="s1.5.f"> |
| <h4 class="subsect">(f) <span class="title">Qualified tsuper</span><a class="img" href="s1.5.f.html" title="PermaLink to (f) Qualified tsuper"><img style="vertical-align:text-top;margin-left:5px;" src="../images/permalink.png" |
| alt="" /></a></h4> |
| <p>A role in a nested team may qualify the keyword <code>tsuper</code> (see <a href="s1.3.1.f.html" title="§1.3.1.(f) tsuper" class="sect">§1.3.1.(f)</a> above) by a type name |
| in order to select among different implicit super classes. |
| A term <code>OuterTeam.tsuper</code> evaluates to a corresponding implicit super class |
| within the context of the explicit super-class (here: <code>SuperOuter</code>) of the enclosing team "<code>OuterTeam</code>". |
| A method call <code>OuterTeam.tsuper.m()</code> |
| evaluates to the method version within <code>SuperOuter</code> that best corresponds to the current method containing the tsuper-call. |
| |
| </p> |
| <div class="codecomment"> |
| <ul> |
| <li>In the above example (<a href="#l1.5" class="listing">Listing 1.5</a>) line 28 selects the method version |
| within the superclass of <code>RoleAndTeamSub</code> (i.e., within <code>RoleAndTeam</code>), |
| resolving to <code>OuterTeam.RoleAndTeam.InnerRole.foo()</code>. |
| </li> |
| <li>Line 29 selects a corresponding method from the context of <code>SuperOuter</code> resolving to <code>SuperOuter.RoleAndTeamSub.InnerRole.foo()</code> |
| which has the same semantics as an unqualified <code>tsuper</code> call would have. |
| |
| </li> |
| </ul> |
| </div> |
| </div> |
| </div> |
| <table class="nav"> |
| <tr> |
| <td class="back"><a href="s1.4.html" rel="prev"><< §1.4 Name clashes</a></td> |
| <td class="top"><a href="index.html" rel="contents">↑ Table of Contents ↑</a></td> |
| <td class="next"></td> |
| </tr> |
| </table> |
| <div class="breadcrumb"><a class="nav" href="s1.html" rel="section">§1 Teams and Roles</a></div> |
| </div> |
| <div id="footer"> |
| <hr /><a class="w3c img" href="http://jigsaw.w3.org/css-validator/check/referer" |
| shape="rect"><img src="../images/valid-css2-blue.png" alt="Valid CSS!" height="31" width="88" /></a><a class="w3c img" href="http://validator.w3.org/check?uri=referer" shape="rect"><img src="../images/valid-xhtml10-blue.png" alt="Valid XHTML 1.0 Strict" height="31" |
| width="88" /></a><address>© Stephan Herrmann, Christine Hundt, Marco Mosconi</address> |
| OT/J version 1.3 — last modified: 2011-05-15 |
| </div> |
| </body> |
| </html> |