org.apache.mahout.common.StringTuple.java Source code

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Here is the source code for org.apache.mahout.common.StringTuple.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.mahout.common;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Collections;
import java.util.List;

import com.google.common.collect.Lists;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.WritableComparable;

/**
 * An Ordered List of Strings which can be used in a Hadoop Map/Reduce Job
 */
public final class StringTuple implements WritableComparable<StringTuple> {

    private List<String> tuple = Lists.newArrayList();

    public StringTuple() {
    }

    public StringTuple(String firstEntry) {
        add(firstEntry);
    }

    public StringTuple(Iterable<String> entries) {
        for (String entry : entries) {
            add(entry);
        }
    }

    public StringTuple(String[] entries) {
        for (String entry : entries) {
            add(entry);
        }
    }

    /**
     * add an entry to the end of the list
     * 
     * @param entry
     * @return true if the items get added
     */
    public boolean add(String entry) {
        return tuple.add(entry);
    }

    /**
     * Fetches the string at the given location
     * 
     * @param index
     * @return String value at the given location in the tuple list
     */
    public String stringAt(int index) {
        return tuple.get(index);
    }

    /**
     * Replaces the string at the given index with the given newString
     * 
     * @param index
     * @param newString
     * @return The previous value at that location
     */
    public String replaceAt(int index, String newString) {
        return tuple.set(index, newString);
    }

    /**
     * Fetch the list of entries from the tuple
     * 
     * @return a List containing the strings in the order of insertion
     */
    public List<String> getEntries() {
        return Collections.unmodifiableList(this.tuple);
    }

    /**
     * Returns the length of the tuple
     * 
     * @return length
     */
    public int length() {
        return this.tuple.size();
    }

    @Override
    public String toString() {
        return tuple.toString();
    }

    @Override
    public int hashCode() {
        return tuple.hashCode();
    }

    @Override
    public boolean equals(Object obj) {
        if (this == obj) {
            return true;
        }
        if (obj == null) {
            return false;
        }
        if (getClass() != obj.getClass()) {
            return false;
        }
        StringTuple other = (StringTuple) obj;
        if (tuple == null) {
            if (other.tuple != null) {
                return false;
            }
        } else if (!tuple.equals(other.tuple)) {
            return false;
        }
        return true;
    }

    @Override
    public void readFields(DataInput in) throws IOException {
        int len = in.readInt();
        tuple = Lists.newArrayListWithCapacity(len);
        Text value = new Text();
        for (int i = 0; i < len; i++) {
            value.readFields(in);
            tuple.add(value.toString());
        }
    }

    @Override
    public void write(DataOutput out) throws IOException {
        out.writeInt(tuple.size());
        Text value = new Text();
        for (String entry : tuple) {
            value.set(entry);
            value.write(out);
        }
    }

    @Override
    public int compareTo(StringTuple otherTuple) {
        int thisLength = length();
        int otherLength = otherTuple.length();
        int min = Math.min(thisLength, otherLength);
        for (int i = 0; i < min; i++) {
            int ret = this.tuple.get(i).compareTo(otherTuple.stringAt(i));
            if (ret != 0) {
                return ret;
            }
        }
        if (thisLength < otherLength) {
            return -1;
        } else if (thisLength > otherLength) {
            return 1;
        } else {
            return 0;
        }
    }

}