IntWritableCache.java

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/*******************************************************************************
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use these files 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.
 *
 * Copyright 2014 - Juan Pino, Aurelien Waite, William Byrne
 *******************************************************************************/
package uk.ac.cam.eng.extraction.hadoop.datatypes;

import java.io.DataInput;
import java.io.IOException;

import org.apache.hadoop.io.IntWritable;

public class IntWritableCache {
        private static final int low = -128;
        private static final int high = 127;
        private static final IntWritable cache[];

        private static class ImmutableIntWritable extends IntWritable {

                boolean set = false;

                ImmutableIntWritable(int i) {
                        super(i);
                }

                @Override
                public void set(int value) {
                        if (set) {
                                throw new UnsupportedOperationException();
                        }
                        set = true;
                        super.set(value);
                }

                @Override
                public void readFields(DataInput in) throws IOException {
                        throw new UnsupportedOperationException();
                }
        }

        static {
                cache = new IntWritable[(high - low) + 1];
                int j = low;
                for (int k = 0; k < cache.length; k++)
                        cache[k] = new ImmutableIntWritable(j++);
        }

        private IntWritableCache() {
        }

        public static IntWritable createIntWritable(int i) {
                if (i >= low && i <= high)
                        return cache[i + (-low)];
                return new IntWritable(i);
        }
}