java.util.Set添加和删除方法签名差异

当我在JDK中看到Set.java文件时，

/**
 *
 * <p>This interface is a member of the
 * <a href="{@docRoot}/../technotes/guides/collections/index.html">
 * Java Collections Framework</a>.
 *
 * @param <E> the type of elements maintained by this set
 *
 * @author  Josh Bloch
 * @author  Neal Gafter
 * @see Collection
 * @see List
 * @see SortedSet
 * @see HashSet
 * @see TreeSet
 * @see AbstractSet
 * @see Collections#singleton(java.lang.Object)
 * @see Collections#EMPTY_SET
 * @since 1.2
 */
public interface Set<E> extends Collection<E> {
    /**
     * @param e element to be added to this set
     * @return <tt>true</tt> if this set did not already contain the specified
     *         element
     * @throws UnsupportedOperationException if the <tt>add</tt> operation
     *         is not supported by this set
     * @throws ClassCastException if the class of the specified element
     *         prevents it from being added to this set
     * @throws NullPointerException if the specified element is null and this
     *         set does not permit null elements
     * @throws IllegalArgumentException if some property of the specified element
     *         prevents it from being added to this set
     */
    boolean add(E e);

     /**
     * @param o object to be removed from this set, if present
     * @return <tt>true</tt> if this set contained the specified element
     * @throws ClassCastException if the type of the specified element
     *         is incompatible with this set
     * (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws NullPointerException if the specified element is null and this
     *         set does not permit null elements
     * (<a href="Collection.html#optional-restrictions">optional</a>)
     * @throws UnsupportedOperationException if the <tt>remove</tt> operation
     *         is not supported by this set
     */
    boolean remove(Object o);

    //other methods
}

我不明白，为什么add方法正在采取E参数和remove方法正在采取Object参数作为输入参数？

任何帮助或参考链接来理解这种行为将不胜感激。

因为你的 Set 总是返回 E，但你可能想检查 Set 中是否有一个对象（不一定是 E）。