/*
* Cloud9: A MapReduce Library for Hadoop
*
* 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 tw.org.nchc.tuple;
import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.ArrayList;
import org.apache.hadoop.io.WritableComparable;
/**
*
* Class that represents an array list in Hadoop's data type system. It extends ArrayList class,
* hence supports all services provided by ArrayList.
* Elements in the list must be homogeneous and must implement Hadoop's Writable interface.
* This class, combined with {@link Tuple}, allows the user to
* define arbitrarily complex data structures.
*
*
* @see Tuple
* @param
* type of list element
*/
public class ArrayListWritableComparable extends ArrayList implements WritableComparable{
private static final long serialVersionUID = 1L;
/**
* Creates an ArrayListWritable object.
*/
public ArrayListWritableComparable() {
super();
}
/**
* Creates an ArrayListWritableComparable object from a regular ArrayList.
*/
public ArrayListWritableComparable(ArrayList array) {
super(array);
}
/**
* Deserializes the array.
*
* @param in
* source for raw byte representation
*/
@SuppressWarnings("unchecked")
public void readFields(DataInput in) throws IOException {
this.clear();
int numFields = in.readInt();
if(numFields==0) return;
String className = in.readUTF();
E obj;
try {
Class c = Class.forName(className);
for (int i = 0; i < numFields; i++) {
obj = (E) c.newInstance();
obj.readFields(in);
this.add(obj);
}
} catch (ClassNotFoundException e) {
e.printStackTrace();
} catch (IllegalAccessException e) {
e.printStackTrace();
} catch (InstantiationException e) {
e.printStackTrace();
}
}
/**
* Serializes this Tuple.
*
* @param out
* where to write the raw byte representation
*/
public void write(DataOutput out) throws IOException {
out.writeInt(this.size());
if(size()==0) return;
E obj=get(0);
out.writeUTF(obj.getClass().getCanonicalName());
for (int i = 0; i < size(); i++) {
obj = get(i);
if (obj == null) {
throw new IOException("Cannot serialize null fields!");
}
obj.write(out);
}
}
/**
*
* Defines a natural sort order for the ListWritable class. Following
* standard convention, this method returns a value less than zero, a value
* greater than zero, or zero if this ListWritable should be sorted before,
* sorted after, or is equal to obj. The sort order is
* defined as follows:
*
*
*
*
Each element in the list is compared sequentially from first to
* last.
*
Lists are sorted with respect to the natural order of the current
* list element under consideration, by calling its compareTo
* method.
*
If the current list elements are equal, the next set of elements are
* considered.
*
If all compared elements are equal, but lists are different lengths,
* the shorter list is sorted first.
*
If all list elements are equal and the lists are equal in length,
* then the lists are considered equal
*
*
* @return a value less than zero, a value greater than zero, or zero if
* this Tuple should be sorted before, sorted after, or is equal to
* obj.
*/
public int compareTo(Object obj) {
ArrayListWritableComparable> that = (ArrayListWritableComparable>) obj;
// iterate through the fields
for (int i = 0; i < this.size(); i++) {
// sort shorter list first
if (i >= that.size())
return 1;
@SuppressWarnings("unchecked")
Comparable