LinkedList里的方法及其作用

push：

/**
     * Pushes an element onto the stack represented by this list.  In other
     * words, inserts the element at the front of this list.
     *
     * <p>This method is equivalent to {@link #addFirst}.
     *
     * @param e the element to push
     * @since 1.6
     */
    public void push(E e) {
        addFirst(e);
    }

 

 

offer：

/**
     * Adds the specified element as the tail (last element) of this list.
     *在集合序列单排序后把指定元素添加到最后一个位置。
     * @param e the element to add
     * @return {@code true} (as specified by {@link Queue#offer})
     * @since 1.5
     */
    public boolean offer(E e) {
        return add(e);
    }

books.push("a"); //把a元素插入到集合中，从0开始；

 

offerFirst：

 /**
     * Inserts the specified element at the front of this list.

     *在集合序单中的最前面插入指定元素。
     *
     * @param e the element to insert
     * @return {@code true} (as specified by {@link Deque#offerFirst})
     * @since 1.6
     */
    public boolean offerFirst(E e) {
        addFirst(e);
        return true;
    }