asterix-om/src/main/java/edu/uci/ics/asterix/om/base/ANull.java

/*
 * Copyright 2009-2011 by The Regents of the University of California
 * 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 from
 * 
 *     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 edu.uci.ics.asterix.om.base;

import edu.uci.ics.asterix.common.exceptions.AsterixException;
import edu.uci.ics.asterix.om.types.BuiltinType;
import edu.uci.ics.asterix.om.types.IAType;
import edu.uci.ics.asterix.om.visitors.IOMVisitor;

// We should avoid representing nulls explicitly. This class is for cases when it is
// harder not to.
public class ANull implements IAObject {

    private ANull() {
    }

    public final static ANull NULL = new ANull();

    @Override
    public void accept(IOMVisitor visitor) throws AsterixException {
        visitor.visitANull(this);
    }

    @Override
    public IAType getType() {
        return BuiltinType.ANULL;
    }

    @Override
    public boolean deepEqual(IAObject obj) {
        return obj == this;
    }

    @Override
    public int hash() {
        return 0;
    }

    @Override
    public String toString() {
        return "null";
    }
}