com.google.gwt.json.client.JSONNull.java Source code

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Here is the source code for com.google.gwt.json.client.JSONNull.java

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/*
 * Copyright 2008 Google Inc.
 * 
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 * 
 * http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.gwt.json.client;

import com.google.gwt.core.client.JavaScriptObject;

/**
 * Represents the JSON <code>null</code> value.
 */
public class JSONNull extends JSONValue {

    private static final JSONNull instance = new JSONNull();

    /**
     * Returns the singleton null-valued JSON object.
     */
    public static JSONNull getInstance() {
        return instance;
    }

    /**
     * Called from {@link #getUnwrapper()}. 
     */
    private static JavaScriptObject unwrap() {
        return null;
    }

    /**
     * There should only be one null value.
     */
    private JSONNull() {
    }

    /**
     * Returns <code>this</code>, as this is a JSONNull.
     */
    @Override
    public JSONNull isNull() {
        return this;
    }

    /**
     * Returns "null" to allow for formatting <code>null</code> values.
     */
    @Override
    public String toString() {
        return "null";
    }

    @Override
    native JavaScriptObject getUnwrapper() /*-{
                                           return @com.google.gwt.json.client.JSONNull::unwrap();
                                           }-*/;

}