Java example source code file (SmallSet.java)

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abstractset, hashset, iterator, nosuchelementexception, override, smallset, util

The SmallSet.java Java example source code

/*
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 * This code is free software; you can redistribute it and/or modify it
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 * published by the Free Software Foundation.  Oracle designates this
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 * by Oracle in the LICENSE file that accompanied this code.
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 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
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/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file:
 *
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
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 *    contributors may be used to endorse or promote products derived from
 *    this software without specific prior written permission.
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 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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package jdk.internal.org.objectweb.asm.tree.analysis;

import java.util.AbstractSet;
import java.util.HashSet;
import java.util.Iterator;
import java.util.NoSuchElementException;
import java.util.Set;

/**
 * A set of at most two elements.
 *
 * @author Eric Bruneton
 */
class SmallSet<E> extends AbstractSet implements Iterator {

    // if e1 is null, e2 must be null; otherwise e2 must be different from e1

    E e1, e2;

    static final <T> Set emptySet() {
        return new SmallSet<T>(null, null);
    }

    SmallSet(final E e1, final E e2) {
        this.e1 = e1;
        this.e2 = e2;
    }

    // -------------------------------------------------------------------------
    // Implementation of inherited abstract methods
    // -------------------------------------------------------------------------

    @Override
    public Iterator<E> iterator() {
        return new SmallSet<E>(e1, e2);
    }

    @Override
    public int size() {
        return e1 == null ? 0 : (e2 == null ? 1 : 2);
    }

    // -------------------------------------------------------------------------
    // Implementation of the Iterator interface
    // -------------------------------------------------------------------------

    public boolean hasNext() {
        return e1 != null;
    }

    public E next() {
        if (e1 == null) {
            throw new NoSuchElementException();
        }
        E e = e1;
        e1 = e2;
        e2 = null;
        return e;
    }

    public void remove() {
    }

    // -------------------------------------------------------------------------
    // Utility methods
    // -------------------------------------------------------------------------

    Set<E> union(final SmallSet s) {
        if ((s.e1 == e1 && s.e2 == e2) || (s.e1 == e2 && s.e2 == e1)) {
            return this; // if the two sets are equal, return this
        }
        if (s.e1 == null) {
            return this; // if s is empty, return this
        }
        if (e1 == null) {
            return s; // if this is empty, return s
        }
        if (s.e2 == null) { // s contains exactly one element
            if (e2 == null) {
                return new SmallSet<E>(e1, s.e1); // necessarily e1 != s.e1
            } else if (s.e1 == e1 || s.e1 == e2) { // s is included in this
                return this;
            }
        }
        if (e2 == null) { // this contains exactly one element
            // if (s.e2 == null) { // cannot happen
            // return new SmallSet(e1, s.e1); // necessarily e1 != s.e1
            // } else
            if (e1 == s.e1 || e1 == s.e2) { // this in included in s
                return s;
            }
        }
        // here we know that there are at least 3 distinct elements
        HashSet<E> r = new HashSet(4);
        r.add(e1);
        if (e2 != null) {
            r.add(e2);
        }
        r.add(s.e1);
        if (s.e2 != null) {
            r.add(s.e2);
        }
        return r;
    }
}