org.apache.hadoop.io.ArrayWritable Maven / Gradle / Ivy
/**
* 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.hadoop.io;
import java.io.*;
import java.lang.reflect.Array;
/**
* A Writable for arrays containing instances of a class. The elements of this
* writable must all be instances of the same class. If this writable will be
* the input for a Reducer, you will need to create a subclass that sets the
* value to be of the proper type.
*
* For example:
*
* public class IntArrayWritable extends ArrayWritable {
* public IntArrayWritable() {
* super(IntWritable.class);
* }
* }
*
*/
public class ArrayWritable implements Writable {
private Class extends Writable> valueClass;
private Writable[] values;
public ArrayWritable(Class extends Writable> valueClass) {
if (valueClass == null) {
throw new IllegalArgumentException("null valueClass");
}
this.valueClass = valueClass;
}
public ArrayWritable(Class extends Writable> valueClass, Writable[] values) {
this(valueClass);
this.values = values;
}
public ArrayWritable(String[] strings) {
this(UTF8.class, new Writable[strings.length]);
for (int i = 0; i < strings.length; i++) {
values[i] = new UTF8(strings[i]);
}
}
public Class getValueClass() {
return valueClass;
}
public String[] toStrings() {
String[] strings = new String[values.length];
for (int i = 0; i < values.length; i++) {
strings[i] = values[i].toString();
}
return strings;
}
public Object toArray() {
Object result = Array.newInstance(valueClass, values.length);
for (int i = 0; i < values.length; i++) {
Array.set(result, i, values[i]);
}
return result;
}
public void set(Writable[] values) { this.values = values; }
public Writable[] get() { return values; }
public void readFields(DataInput in) throws IOException {
values = new Writable[in.readInt()]; // construct values
for (int i = 0; i < values.length; i++) {
Writable value = WritableFactories.newInstance(valueClass);
value.readFields(in); // read a value
values[i] = value; // store it in values
}
}
public void write(DataOutput out) throws IOException {
out.writeInt(values.length); // write values
for (int i = 0; i < values.length; i++) {
values[i].write(out);
}
}
}