org.apache.apex.malhar.lib.appdata.schemas.Fields.java Source code

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Here is the source code for org.apache.apex.malhar.lib.appdata.schemas.Fields.java

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/**
 * 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.apex.malhar.lib.appdata.schemas;

import java.io.Serializable;
import java.util.Collection;
import java.util.List;
import java.util.Set;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;

/**
 * This is a somewhat vacuous class for managing field names for AppData schemas and queries.
 * Its function is to maintain a set of field names with no null values. It also maintains a list
 * of field names to increase iteration speed.
 * @since 3.0.0
 */
public class Fields implements Serializable {
    private static final long serialVersionUID = 201506251241L;

    /**
     * Set of field names.
     */
    private Set<String> fields;
    /**
     * List of field names.
     */
    private List<String> fieldsList;

    /**
     * Creats an empty set of fields.
     */
    public Fields() {
    }

    /**
     * Creates a set of fields from the given collection of fields.
     * @param fields The collection object to create this {@link Fields} object from.
     */
    public Fields(Collection<String> fields) {
        this.fields = Sets.newLinkedHashSet();

        for (String field : fields) {
            Preconditions.checkNotNull(field);
            if (!this.fields.add(field)) {
                throw new IllegalArgumentException("Duplicate field: " + field);
            }
        }

        fieldsList = Lists.newArrayList();
        fieldsList.addAll(fields);
    }

    /**
     * This gets the set of fields managed by this {@link Fields} object.
     * @return The set of fields managed by this {@link Fields} object.
     */
    public Set<String> getFields() {
        return fields;
    }

    /**
     * Gets the list of fields managed by this {@link Fields} object.
     * @return The list of fields managed by this {@link Fields} object.
     */
    public List<String> getFieldsList() {
        return fieldsList;
    }

    @Override
    public String toString() {
        return "Fields{" + "fields=" + fields + '}';
    }

    @Override
    public int hashCode() {
        int hash = 7;
        hash = 43 * hash + (this.fields != null ? this.fields.hashCode() : 0);
        return hash;
    }

    @Override
    public boolean equals(Object obj) {
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        final Fields other = (Fields) obj;
        if (this.fields != other.fields && (this.fields == null || !this.fields.equals(other.fields))) {
            return false;
        }
        return true;
    }

    private static final Logger LOG = LoggerFactory.getLogger(Fields.class);
}