The first and last was introduced in 1. When you iterate over a LinkedHashSet, you will get the elements in the order you inserted. Inside the while loop you call the Iterator next method of the Iterator interface to obtain the next element pointed to by the Iterator. Further, this method allows precise control over the runtime type of the output array, and may, under certain circumstances, be used to save allocation costs. Remember, the original list has 4 elements with indexes from 0 to 3. After the clear method has been called, the List will be completely empty. LinkedList has getFirst and getLast method to retrieve first and last element from LinkedList in Java. If you're interested I can provide this source. Another difference between the two is the exception that could be possibly thrown. ArrayList is index based data structure. Generic Lists By default you can put any Object into a List, but from Java 5, Java Generics makes it possible to limit the types of object you can insert into a List.
An ordered collection also known as a sequence. The user of this interface has precise control over where in the list each element is inserted. The user can access elements by their integer index position in the listand search for elements in the list. Unlike sets, lists typically allow duplicate elements. More formally, lists typically allow pairs of elements e1 and e2 such that e1. It is not inconceivable that someone might wish to implement a list that prohibits duplicates, by throwing runtime exceptions when the user attempts to insert them, but we expect this usage to be rare. The List interface places additional stipulations, beyond those specified in the Collection java list get first element, on the contracts of the iterator, add, remove, equals, and hashCode methods. Declarations for other inherited methods are also included here for convenience. The List interface provides four methods for positional indexed access to list elements. Lists like Java arrays are zero based. Note that these operations may execute in time proportional to the index value for some implementations the LinkedList class, for example. Thus, iterating over the elements in a list is typically preferable to indexing through it if the caller does not know the implementation. The List interface provides a special iterator, called a ListIterator, that allows element insertion and replacement, and bidirectional access in addition to the normal operations that the Iterator interface provides. A method is provided to obtain a list iterator that starts at a specified position in the list. The List interface provides two methods to search for a specified object. From a performance standpoint, these methods should be used with caution. In many implementations they will perform costly linear searches. The List interface provides two methods to efficiently insert and remove multiple elements at an arbitrary point in the list. Note: While it is permissible for lists to contain themselves as elements, extreme caution is advised: the equals and hashCode methods are no longer well defined on such a list. Some list implementations have restrictions on the elements that they may contain. For example, some implementations prohibit null elements, and some have restrictions on the types of their elements. Attempting to add an ineligible element throws an unchecked exception, typically NullPointerException or ClassCastException. Attempting to query the presence of an ineligible element may throw an exception, or it may simply return false; some implementations will exhibit the former behavior and some will exhibit the latter. More generally, attempting an operation on an ineligible element whose completion would not result in the insertion of an ineligible element into the list may throw an java list get first element or it may succeed, at the option of the implementation. This interface is a member of the. In other words, this method must allocate a new array even if this list is backed by an array. The caller is thus free to modify the returned array. If the list fits in the specified array, it is returned therein. Otherwise, a new array is allocated with the runtime type of the specified array and the size of this list. If the list fits in the specified array with room to spare i. This is useful in determining the length of the list only if the caller knows that the list does not contain any null elements. Further, this method allows precise control over the runtime type java list get first element the output array, and may, under certain circumstances, be used to save allocation costs. Suppose x is a list known to contain only strings. Specified by: in interface Parameters: a - the array into which the elements of this list are to be stored, if it is big enough; otherwise, a new array of the same runtime type is allocated for this purpose. Lists that support this operation may place limitations on what elements may be added to this list. In particular, some lists will refuse to add null elements, and others will impose restrictions on the type of elements that may be added. List classes should clearly specify in their documentation any restrictions on what elements may be added. If this list does not contain the element, it is unchanged. Returns true if this list contained the specified element or equivalently, if this list changed as a result of the call. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. Note that this will occur if the specified collection is this list, and it's nonempty. Shifts the element currently at that position if any and any subsequent elements to the right increases their indices. The new elements will appear in this list in the order that they java list get first element returned by the specified collection's iterator. The behavior of this operation is undefined if the specified collection is modified while the operation is in progress. Note that this will occur if the specified collection is this list, and it's nonempty. In other words, removes from this list all of its elements that are not contained in the specified collection. Returns true if and only if the specified object is also a list, both lists have the same size, and all corresponding pairs of elements in the two lists are equal. In other words, two lists are defined to be equal if they contain the same elements in the same order. This definition ensures that the equals method works properly across different implementations of the List interface. Shifts the element currently at that position if any and any subsequent elements to the right adds one to their indices. Shifts any subsequent elements to the left subtracts one from their indices. Returns the element that was removed from the list. The specified index indicates the first element that would be returned by an initial call to. An initial call to would return the element with the specified index minus one. If fromIndex and toIndex are equal, the returned list is empty. The returned list is backed by this list, so non-structural changes in the returned list are reflected in this list, and vice-versa. The returned list supports all of the optional list operations supported by this list. This method eliminates the need for explicit range operations of the sort that commonly exist for arrays. Any operation that expects a list can be used as a range operation by passing a subList view instead of a whole list. For example, the following idiom removes a range of elements from a list: list. The semantics of the list returned by this method become undefined if the backing list i. Structural modifications are those that change the size of this list, or otherwise perturb it in such a fashion that iterations in progress may yield incorrect results.
