HashSet和HashMap的关系

最新推荐文章于 2023-12-25 09:15:00 发布

最新推荐文章于 2023-12-25 09:15:00 发布 · 123 阅读

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#java

本文深入探讨了Java中HashSet类如何利用HashMap实现高效性，详细解释了两者之间的区别与联系，帮助开发者更好地理解和使用集合框架。

public class HashSet<E>
    extends AbstractSet<E>
    implements Set<E>, Cloneable, java.io.Serializable
{
    static final long serialVersionUID = -5024744406713321676L;

    private transient HashMap<E,Object> map;

    // Dummy value to associate with an Object in the backing Map
    private static final Object PRESENT = new Object();

    /**
     * Constructs a new, empty set; the backing <tt>HashMap</tt> instance has
     * default initial capacity (16) and load factor (0.75).
     */
    public HashSet() {
	map = new HashMap<E,Object>();
    }
.........
    /**
     * Returns an iterator over the elements in this set.  The elements
     * are returned in no particular order.
     *
     * @return an Iterator over the elements in this set
     * @see ConcurrentModificationException
     */
    public Iterator<E> iterator() {
	return map.keySet().iterator();
    }

我貌似也遇到过这样的面试官，问这两者的关系，原来是HashSet就是用的HashMap啊，只是省略了value，只用了key