com.twitter.aurora.scheduler.base.Numbers.java Source code

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Here is the source code for com.twitter.aurora.scheduler.base.Numbers.java

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/*
 * Copyright 2013 Twitter, Inc.
 *
 * 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 com.twitter.aurora.scheduler.base;

import java.util.Set;

import com.google.common.collect.ImmutableSet;
import com.google.common.collect.Iterators;
import com.google.common.collect.PeekingIterator;
import com.google.common.collect.Range;
import com.google.common.collect.Sets;

/**
 * Utility class for working with numbers.
 */
public final class Numbers {

    private Numbers() {
        // Utility class.
    }

    /**
     * Converts a set of integers into a set of contiguous closed ranges that equally represent the
     * input integers.
     * <p>
     * The resulting ranges will be in ascending order.
     *
     * @param values Values to transform to ranges.
     * @return Closed ranges with identical members to the input set.
     */
    public static Set<Range<Integer>> toRanges(Iterable<Integer> values) {
        ImmutableSet.Builder<Range<Integer>> builder = ImmutableSet.builder();

        PeekingIterator<Integer> iterator = Iterators.peekingIterator(Sets.newTreeSet(values).iterator());

        // Build ranges until there are no numbers left.
        while (iterator.hasNext()) {
            // Start a new range.
            int start = iterator.next();
            int end = start;
            // Increment the end until the range is non-contiguous.
            while (iterator.hasNext() && (iterator.peek() == (end + 1))) {
                end++;
                iterator.next();
            }

            builder.add(Range.closed(start, end));
        }

        return builder.build();
    }
}