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A Java Optimization Framework
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package soot.util;

/*-
 * #%L
 * Soot - a J*va Optimization Framework
 * %%
 * Copyright (C) 1997 - 1999 Raja Vallee-Rai
 * %%
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as
 * published by the Free Software Foundation, either version 2.1 of the
 * License, or (at your option) any later version.
 * 
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Lesser Public License for more details.
 * 
 * You should have received a copy of the GNU General Lesser Public
 * License along with this program.  If not, see
 * .
 * #L%
 */

import java.util.AbstractSet;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * Provides an implementation of the Set interface using an array.
 * 
 * @param 
 */
public class ArraySet extends AbstractSet {
  private static final int DEFAULT_SIZE = 8;

  private int numElements;
  private int maxElements;
  private E[] elements;

  public ArraySet(int size) {
    maxElements = size;
    @SuppressWarnings("unchecked")
    E[] newElements = (E[]) new Object[size];
    elements = newElements;
    numElements = 0;
  }

  public ArraySet() {
    this(DEFAULT_SIZE);
  }

  /**
   * Create a set which contains the given elements.
   */
  public ArraySet(E[] elements) {
    this();
    for (E element : elements) {
      add(element);
    }
  }

  @Override
  final public void clear() {
    numElements = 0;
  }

  @Override
  final public boolean contains(Object obj) {
    for (int i = 0; i < numElements; i++) {
      if (elements[i].equals(obj)) {
        return true;
      }
    }
    return false;
  }

  /**
   * Add an element without checking whether it is already in the set. It is up to the caller to guarantee that it isn't.
   */
  final public boolean addElement(E e) {
    if (e == null) {
      throw new RuntimeException("oops");
    }
    // Expand array if necessary
    if (numElements == maxElements) {
      doubleCapacity();
    }

    // Add element
    elements[numElements++] = e;
    return true;
  }

  @Override
  final public boolean add(E e) {
    if (e == null) {
      throw new RuntimeException("oops");
    }
    if (contains(e)) {
      return false;
    } else {
      // Expand array if necessary
      if (numElements == maxElements) {
        doubleCapacity();
      }

      // Add element
      elements[numElements++] = e;
      return true;
    }
  }

  @Override
  final public boolean addAll(Collection s) {
    if (s instanceof ArraySet) {
      boolean ret = false;
      ArraySet as = (ArraySet) s;
      for (E elem : as.elements) {
        ret |= add(elem);
      }
      return ret;
    } else {
      return super.addAll(s);
    }
  }

  @Override
  final public int size() {
    return numElements;
  }

  @Override
  final public Iterator iterator() {
    return new ArrayIterator();
  }

  private class ArrayIterator implements Iterator {
    int nextIndex;

    ArrayIterator() {
      nextIndex = 0;
    }

    @Override
    final public boolean hasNext() {
      return nextIndex < numElements;
    }

    @Override
    final public E next() throws NoSuchElementException {
      if (!(nextIndex < numElements)) {
        throw new NoSuchElementException();
      } else {
        return elements[nextIndex++];
      }
    }

    @Override
    final public void remove() throws NoSuchElementException {
      if (nextIndex == 0) {
        throw new NoSuchElementException();
      } else {
        removeElementAt(nextIndex - 1);
        nextIndex = nextIndex - 1;
      }
    }
  }

  private void removeElementAt(int index) {
    // Handle simple case
    if (index == numElements - 1) {
      numElements--;
      return;
    }

    // Else, shift over elements
    System.arraycopy(elements, index + 1, elements, index, numElements - (index + 1));
    numElements--;
  }

  private void doubleCapacity() {
    // plus one to ensure that we have at least one element
    int newSize = maxElements * 2 + 1;

    @SuppressWarnings("unchecked")
    E[] newElements = (E[]) new Object[newSize];

    System.arraycopy(elements, 0, newElements, 0, numElements);
    elements = newElements;
    maxElements = newSize;
  }

  @Override
  final public E[] toArray() {
    @SuppressWarnings("unchecked")
    E[] array = (E[]) new Object[numElements];

    System.arraycopy(elements, 0, array, 0, numElements);
    return array;
  }

  @Override
  final public  T[] toArray(T[] array) {
    if (array.length < numElements) {
      @SuppressWarnings("unchecked")
      T[] ret = (T[]) Arrays.copyOf(elements, numElements, array.getClass());
      return ret;
    } else {
      System.arraycopy(elements, 0, array, 0, numElements);
      if (array.length > numElements) {
        array[numElements] = null;
      }
      return array;
    }
  }

  final public Object[] getUnderlyingArray() {
    return elements;
  }
}