SchemaNameComparator.java

/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.metamodel;

import java.util.Comparator;

/**
 * Comparator for comparing schema names.
 */
class SchemaNameComparator implements Comparator<String> {

    private static Comparator<? super String> _instance = new SchemaNameComparator();

    public static Comparator<? super String> getInstance() {
        return _instance;
    }

    private SchemaNameComparator() {
    }

    public int compare(String o1, String o2) {
        if (o1 == null && o2 == null) {
            return 0;
        }
        if (o1 == null) {
            return -1;
        }
        if (o2 == null) {
            return 1;
        }
        if (MetaModelHelper.isInformationSchema(o1)) {
            return -1;
        }
        if (MetaModelHelper.isInformationSchema(o2)) {
            return 1;
        }
        return o1.compareTo(o2);
    }

}