* will be expanded to DEFAULT_CAPACITY when the first element is added.*/transientObject[] elementData;//non-private to simplify nested class access ArrayList的容量就是数组的长度。 任何elementData等于DEFAULTCAPACITY_EMPTY_ELEMENTDATA的空ArrayList,当其第一个元素被添加进来时,elementData的长度将被扩展为DE...
In this tutorial we look at the history of element iteration in Java. From the early days of Java until Java 8.
初始化为-1 int lastRet = -1; int expectedModCount = modCount; // 无参构造 Itr() {} public boolean hasNext() { return cursor != size; } @SuppressWarnings("unchecked") public E next() { // 检查是否被修改 checkForComodification(); int...
最后,使用Collections.sort这样的辅助方法并不是一个好主意:它不但使代码变的冗余,也无法为实现List接口的数据结构提供特定(specialized)的高效实现,而且由于Collections.sort方法不属于List接口,用户在阅读List接口的文档时不会察觉在另外的Collections类中还有一个针对List接口的排序(sort())方法。 默认方法可以有效的解...
ArrayList继承了AbstractList接口,实现了List,以及随机访问,可克隆,序列化接口。不是线程安全的,如果需要线程安全,则需要选择其他的类或者使用Collections.synchronizedList(arrayList)允许存储null元素,也允许相同的元素存在。 其底层实际上是数组实现的,那为什么我们使用的时候只管往里面存东西,不用关心其大小呢?因为ArrayLis...
List<String> items = new ArrayList<>(); items.add("coins"); items.add("pens"); items.add("keys"); items.add("sheets"); items.forEach((String name) -> { System.out.println(name); }); } This example revisits the previous list iteration, now using a lambda expression. By replaci...
This reduction, also known in functional circles as a fold, starts with a seed value (0, in this case), and applies the closure to the seed and the first element in the stream, taking the result and storing it as the accumulated value that will be used as the seed for the next ...
Returns an array containing all of the elements in this list in proper sequence (from first to last element). <T> T[]toArray(T[] a) Returns an array containing all of the elements in this list in proper sequence (from first to last element); the runtime type of the returned array ...
An iterator for lists that allows the programmer to traverse the list in either direction, modify the list during iteration, and obtain the iterator's current position in the list. A ListIterator has no current element; its cursor position always lies between the element that would be returned...
An iterator for lists that allows the programmer to traverse the list in either direction, modify the list during iteration, and obtain the iterator's current position in the list. Map<K,V> An object that maps keys to values. Map.Entry<K,V> ...