vector

• The Vector class implements a growable array of objects.
• Like an array, it contains components that can be accessed using an integer index.
• However, the size of a Vector can grow or shrink as needed to accommodate adding and removing items after the Vector has been created. 
• 这个矢量（向量）类实现一个对象的递增（可增长的）数组。
• 像一个数组，它包含能够访问使用整型索引的部分。
• 然而，这个向量类的大小可以增大或缩小根据需要，去适应添加和删除项目在向量类创造之后。