Main.java Source code

Introduction

Here is the source code for Main.java

Source

//package com.java2s;
import java.util.Collection;

import java.util.Iterator;

public class Main {
    /**
     * Used for results of getContainmentRelation
     */
    public static final int ALL_EMPTY = 0, NOT_A_SUPERSET_B = 1, NOT_A_DISJOINT_B = 2, NOT_A_SUBSET_B = 4,
            NOT_A_EQUALS_B = NOT_A_SUBSET_B | NOT_A_SUPERSET_B,
            A_PROPER_SUBSET_OF_B = NOT_A_DISJOINT_B | NOT_A_SUPERSET_B,
            A_PROPER_SUPERSET_B = NOT_A_SUBSET_B | NOT_A_DISJOINT_B,
            A_PROPER_OVERLAPS_B = NOT_A_SUBSET_B | NOT_A_DISJOINT_B | NOT_A_SUPERSET_B;

    /**
     * Assesses all the possible containment relations between collections A and B with one call.<br>
     * Returns an int with bits set, according to a "Venn Diagram" view of A vs B.<br>
     * NOT_A_SUPERSET_B: a - b != {}<br>
     * NOT_A_DISJOINT_B: a * b != {}  // * is intersects<br>
     * NOT_A_SUBSET_B: b - a != {}<br>
     * Thus the bits can be used to get the following relations:<br>
     * for A_SUPERSET_B, use (x & CollectionUtilities.NOT_A_SUPERSET_B) == 0<br>
     * for A_SUBSET_B, use (x & CollectionUtilities.NOT_A_SUBSET_B) == 0<br>
     * for A_EQUALS_B, use (x & CollectionUtilities.NOT_A_EQUALS_B) == 0<br>
     * for A_DISJOINT_B, use (x & CollectionUtilities.NOT_A_DISJOINT_B) == 0<br>
     * for A_OVERLAPS_B, use (x & CollectionUtilities.NOT_A_DISJOINT_B) != 0<br>
     */
    public static int getContainmentRelation(Collection a, Collection b) {
        if (a.size() == 0) {
            return (b.size() == 0) ? ALL_EMPTY : NOT_A_SUPERSET_B;
        } else if (b.size() == 0) {
            return NOT_A_SUBSET_B;
        }
        int result = 0;
        // WARNING: one might think that the following can be short-circuited, by looking at
        // the sizes of a and b. However, this would fail in general, where a different comparator is being
        // used in the two collections. Unfortunately, there is no failsafe way to test for that.
        for (Iterator it = a.iterator(); result != 6 && it.hasNext();) {
            result |= (b.contains(it.next())) ? NOT_A_DISJOINT_B : NOT_A_SUBSET_B;
        }
        for (Iterator it = b.iterator(); (result & 3) != 3 && it.hasNext();) {
            result |= (a.contains(it.next())) ? NOT_A_DISJOINT_B : NOT_A_SUPERSET_B;
        }
        return result;
    }

    /**
     * Get the size of an iterator (number of items in it).
     * @param source
     * @return
     */
    public static int size(Iterator source) {
        int result = 0;
        while (source.hasNext()) {
            source.next();
            ++result;
        }
        return result;
    }
}