|
Java example source code file (Undefined.java)
The Undefined.java Java example source code/* * Copyright (c) 2010, 2013, 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 jdk.nashorn.internal.runtime; import static jdk.nashorn.internal.runtime.ECMAErrors.typeError; import static jdk.nashorn.internal.lookup.Lookup.MH; import java.lang.invoke.MethodHandle; import java.lang.invoke.MethodHandles; import java.lang.invoke.MethodType; import jdk.internal.dynalink.CallSiteDescriptor; import jdk.internal.dynalink.linker.GuardedInvocation; import jdk.internal.dynalink.support.CallSiteDescriptorFactory; import jdk.internal.dynalink.support.Guards; /** * Unique instance of this class is used to represent JavaScript undefined. */ public final class Undefined extends DefaultPropertyAccess { private Undefined() { } private static final Undefined UNDEFINED = new Undefined(); private static final Undefined EMPTY = new Undefined(); // Guard used for indexed property access/set on the Undefined instance private static final MethodHandle UNDEFINED_GUARD = Guards.getIdentityGuard(UNDEFINED); /** * Get the value of {@code undefined}, this is represented as a global singleton * instance of this class. It can always be reference compared * * @return the undefined object */ public static Undefined getUndefined() { return UNDEFINED; } /** * Get the value of {@code empty}. This is represented as a global singleton * instanceof this class. It can always be reference compared. * <p> * We need empty to differentiate behavior in things like array iterators * <p> * @return the empty object */ public static Undefined getEmpty() { return EMPTY; } /** * Get the class name of Undefined * @return "Undefined" */ @SuppressWarnings("static-method") public String getClassName() { return "Undefined"; } @Override public String toString() { return "undefined"; } /** * Lookup the appropriate method for an invoke dynamic call. * @param desc The invoke dynamic callsite descriptor. * @return GuardedInvocation to be invoked at call site. */ public static GuardedInvocation lookup(final CallSiteDescriptor desc) { final String operator = CallSiteDescriptorFactory.tokenizeOperators(desc).get(0); switch (operator) { case "new": case "call": throw lookupTypeError("cant.call.undefined", desc); case "callMethod": throw lookupTypeError("cant.read.property.of.undefined", desc); // NOTE: we support getElem and setItem as JavaScript doesn't distinguish items from properties. Nashorn itself // emits "dyn:getProp:identifier" for "<expr>. Other Java examples (source code examples)Here is a short list of links related to this Java Undefined.java source code file: |
... this post is sponsored by my books ... | |
#1 New Release! |
FP Best Seller |
Copyright 1998-2021 Alvin Alexander, alvinalexander.com
All Rights Reserved.
A percentage of advertising revenue from
pages under the /java/jwarehouse
URI on this website is
paid back to open source projects.