HashSet的实现

Set是由若干个无序且不重复的对象所组成。它既包含Array的运算功能,同时又兼有Hash的高速搜索功能。HashSet是基于HashMap实现的.

      
      java
    

    
1import java.util.Collection;
2import java.util.HashMap;
3import java.util.Iterator;
4import java.util.Set;
5
6public class MySet<E> implements Set<E>{
  private HashMap<E, Object> map;
  private static final Object notUse=new Object();
  
  public MySet() {
      map = new HashMap<E,Object>();
  }
  @Override
  public Iterator<E> iterator() {
      return map.keySet().iterator();
  }
17
  @Override
  public boolean add(E e) {
      return map.put(e, notUse) == null;
  }
22
  @Override
  public boolean addAll(Collection<? extends E> c) {
      return false;
  }
27
  @Override
  public void clear() {
      map.clear();
  }
32
  @Override
  public boolean contains(Object o) {
      return map.containsKey(o);
  }
37
  @Override
  public boolean containsAll(Collection<?> c) {
      return false;
  }
42
  @Override
  public boolean isEmpty() {
      return map.isEmpty();
  }
47
  @Override
  public boolean remove(Object o) {
      return map.remove(o) == notUse;
  }
52
  @Override
  public boolean removeAll(Collection<?> c) {
      return false;
  }
57
  @Override
  public boolean retainAll(Collection<?> c) {
      return false;
  }
62
  @Override
  public int size() {
      return map.size();
  }
67
  @Override
  public Object[] toArray() {
      
      return null;
  }
73
  @Override
  public <T> T[] toArray(T[] a) {
      return null;
  }
78}