jdk/src/java.base/share/classes/java/lang/NamedPackage.java
changeset 36511 9d0388c6b336
child 44545 83b611b88ac8
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/jdk/src/java.base/share/classes/java/lang/NamedPackage.java	Thu Mar 17 19:04:16 2016 +0000
@@ -0,0 +1,90 @@
+/*
+ * Copyright (c) 2016, Oracle and/or its affiliates. All rights reserved.
+ * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
+ *
+ * This code is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.  Oracle designates this
+ * particular file as subject to the "Classpath" exception as provided
+ * by Oracle in the LICENSE file that accompanied this code.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+package java.lang;
+
+import java.lang.module.Configuration;
+import java.lang.module.ModuleReference;
+import java.lang.reflect.Module;
+import java.net.URI;
+
+/**
+ * A NamedPackage represents a package by name in a specific module.
+ *
+ * A class loader will automatically create NamedPackage for each
+ * package when a class is defined.  Package object is lazily
+ * defined until Class::getPackage, Package::getPackage(s), or
+ * ClassLoader::getDefinedPackage(s) method is called.
+ *
+ * NamedPackage allows ClassLoader to keep track of the runtime
+ * packages with minimal footprint and avoid constructing Package
+ * object.
+ */
+class NamedPackage {
+    private final String name;
+    private final Module module;
+
+    NamedPackage(String pn, Module module) {
+        if (pn.isEmpty() && module.isNamed()) {
+            throw new InternalError("unnamed package in  " + module);
+        }
+        this.name = pn.intern();
+        this.module = module;
+    }
+
+    /**
+     * Returns the name of this package.
+     */
+    String packageName() {
+        return name;
+    }
+
+    /**
+     * Returns the module of this named package.
+     */
+    Module module() {
+        return module;
+    }
+
+    /**
+     * Returns the location of the module if this named package is in
+     * a named module; otherwise, returns null.
+     */
+    URI location() {
+        if (module.isNamed() && module.getLayer() != null) {
+            Configuration cf = module.getLayer().configuration();
+            ModuleReference mref
+                = cf.findModule(module.getName()).get().reference();
+            return mref.location().orElse(null);
+        }
+        return null;
+    }
+
+    /**
+     * Creates a Package object of the given name and module.
+     */
+    static Package toPackage(String name, Module module) {
+        return new Package(name, module);
+    }
+}