de.rwhq.btree.Range.java Source code

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Here is the source code for de.rwhq.btree.Range.java

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/*
 * This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License:
 *
 * http://creativecommons.org/licenses/by-nc/3.0/
 *
 * For alternative conditions contact the author.
 *
 * Copyright (c) 2011 "Robin Wenglewski <robin@wenglewski.de>"
 */

package de.rwhq.btree;

import com.google.common.base.Objects;
import com.google.common.collect.Lists;
import com.google.common.collect.Sets;

import java.util.*;

import static com.google.common.base.Preconditions.checkNotNull;

/**
 * Very generic Range object for getting values form the BTree
 *
 * @param <T>
 */
public class Range<T> {
    public static <K> Comparator<Range<K>> createRangeComparator(final Comparator<K> comparator) {
        return new Comparator<Range<K>>() {
            private int compareWithNull(K k1, K k2, boolean nullIsSmallest) {
                if (k1 == null) {
                    if (k2 == null) {
                        return 0;
                    } else {
                        return nullIsSmallest ? -1 : 1;
                    }
                } else if (k2 == null) {
                    return nullIsSmallest ? 1 : -1;
                }

                return comparator.compare(k1, k2);
            }

            @Override
            public int compare(final Range<K> r1, final Range<K> r2) {
                int compareResult = compareWithNull(r1.getFrom(), r2.getFrom(), true);

                if (compareResult != 0)
                    return compareResult;

                return compareWithNull(r1.getTo(), r2.getTo(), false);
            }
        };
    }

    /**
     * merges the given Collection of Ranges by using the provided comparator.
     * 
     * @param ranges
     * @param comparator
     * @param <K>
     * @return
     */
    public static <K> TreeSet<Range<K>> merge(final Collection<Range<K>> ranges, final Comparator<K> comparator) {
        checkNotNull(ranges, "range list must not be null");
        checkNotNull(comparator, "comparator must not be null");

        TreeSet<Range<K>> tmpSet = Sets.newTreeSet(createRangeComparator(comparator));

        tmpSet.addAll(ranges);
        Range<K> last = null;

        Iterator<Range<K>> iterator = tmpSet.iterator();
        while (iterator.hasNext()) {
            Range<K> r = iterator.next();

            if (last == null) {
                last = r;
                continue;
            }

            // only if this to() is larger than last to(), extend to()
            if (last.getTo() != null) {
                if ((r.getFrom() == null || comparator.compare(last.getTo(), r.getFrom()) >= 0)) {
                    if (r.getTo() == null)
                        last.setTo(null);
                    else if (comparator.compare(last.getTo(), r.getTo()) < 0) {
                        last.setTo(r.getTo());
                    }

                    iterator.remove();
                } else { // separate ranges
                    last = r;
                }
            } else {
                iterator.remove();
            }
        }

        return tmpSet;
    }

    private T from;
    private T to;

    private Comparator<T> comparator;

    public Comparator<T> getComparator() {
        return comparator;
    }

    public void setComparator(Comparator<T> comparator) {
        this.comparator = comparator;
    }

    public Range() {
    }

    public Range(final T from, final T to) {
        this(from, to, null);
    }

    public Range(final T from, final T to, final Comparator<T> comparator) {
        this.from = from;
        this.to = to;
        this.comparator = comparator;
    }

    public boolean contains(T obj) {
        return contains(obj, comparator);
    }

    public boolean contains(T obj, Comparator<T> comparator) {
        checkNotNull(obj, "can't check contains on null. Check from/to directly.");
        checkNotNull(comparator, "comparator must not be null for contains() to work");

        return (from == null || comparator.compare(from, obj) <= 0)
                && (to == null || comparator.compare(obj, to) <= 0);
    }

    public T getTo() {
        return to;
    }

    public void setTo(final T to) {
        this.to = to;
    }

    public T getFrom() {
        return from;
    }

    public void setFrom(final T from) {
        this.from = from;
    }

    public String toString() {
        return Objects.toStringHelper(this).add("from", from).add("to", to).toString();
    }

    @Override
    public int hashCode() {
        return Objects.hashCode(from, to);
    }

    @Override
    public boolean equals(final Object obj) {
        if (obj instanceof Range) {
            final Range other = (Range) obj;
            return Objects.equal(from, other.from) && Objects.equal(to, other.to);
        } else {
            return false;
        }
    }
}