| ylbtech-Java-Class-I：java.util.List.java |
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import java.util.ArrayList;
import java.util.List;
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List<Integer> newList = new ArrayList<Integer>();
newList.add(3);
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import java.util.*; public class Test{ public static void main(String[] args) { List<String> list=new ArrayList<String>(); list.add("Hello"); list.add("World"); list.add("HAHAHAHA"); //第一种遍历方法使用foreach遍历List for (String str : list) { //也可以改写for(int i=0;i<list.size();i++)这种形式 System.out.println(str); } //第二种遍历，把链表变为数组相关的内容进行遍历 String[] strArray=new String[list.size()]; list.toArray(strArray); for(int i=0;i<strArray.length;i++) //这里也可以改写为 foreach(String str:strArray)这种形式 { System.out.println(strArray[i]); } //第三种遍历 使用迭代器进行相关遍历 Iterator<String> ite=list.iterator(); while(ite.hasNext())//判断下一个元素之后有值 { System.out.println(ite.next()); } } }
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/* * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved. * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms. * * * * * * * * * * * * * * * * * * * * */ package java.util; import java.util.function.UnaryOperator; /** * An ordered collection (also known as a <i>sequence</i>). 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 list), and search for elements in the list.<p> * * Unlike sets, lists typically allow duplicate elements. More formally, * lists typically allow pairs of elements <tt>e1</tt> and <tt>e2</tt> * such that <tt>e1.equals(e2)</tt>, and they typically allow multiple * null elements if they allow null elements at all. 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.<p> * * The <tt>List</tt> interface places additional stipulations, beyond those * specified in the <tt>Collection</tt> interface, on the contracts of the * <tt>iterator</tt>, <tt>add</tt>, <tt>remove</tt>, <tt>equals</tt>, and * <tt>hashCode</tt> methods. Declarations for other inherited methods are * also included here for convenience.<p> * * The <tt>List</tt> 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 <tt>LinkedList</tt> 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.<p> * * The <tt>List</tt> interface provides a special iterator, called a * <tt>ListIterator</tt>, that allows element insertion and replacement, and * bidirectional access in addition to the normal operations that the * <tt>Iterator</tt> interface provides. A method is provided to obtain a * list iterator that starts at a specified position in the list.<p> * * The <tt>List</tt> 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.<p> * * The <tt>List</tt> interface provides two methods to efficiently insert and * remove multiple elements at an arbitrary point in the list.<p> * * Note: While it is permissible for lists to contain themselves as elements, * extreme caution is advised: the <tt>equals</tt> and <tt>hashCode</tt> * methods are no longer well defined on such a list. * * <p>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 * <tt>NullPointerException</tt> or <tt>ClassCastException</tt>. 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 * exception or it may succeed, at the option of the implementation. * Such exceptions are marked as "optional" in the specification for this * interface. * * <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 in this list * * @author Josh Bloch * @author Neal Gafter * @see Collection * @see Set * @see ArrayList * @see LinkedList * @see Vector * @see Arrays#asList(Object[]) * @see Collections#nCopies(int, Object) * @see Collections#EMPTY_LIST * @see AbstractList * @see AbstractSequentialList * @since 1.2 */ public interface List<E> extends Collection<E> { // Query Operations /** * Returns the number of elements in this list. If this list contains * more than <tt>Integer.MAX_VALUE</tt> elements, returns * <tt>Integer.MAX_VALUE</tt>. * * @return the number of elements in this list */ int size(); /** * Returns <tt>true</tt> if this list contains no elements. * * @return <tt>true</tt> if this list contains no elements */ boolean isEmpty(); /** * Returns <tt>true</tt> if this list contains the specified element. * More formally, returns <tt>true</tt> if and only if this list contains * at least one element <tt>e</tt> such that * <tt>(o==null ? e==null : o.equals(e))</tt>. * * @param o element whose presence in this list is to be tested * @return <tt>true</tt> if this list contains the specified element * @throws ClassCastException if the type of the specified element * is incompatible with this list * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if the specified element is null and this * list does not permit null elements * (<a href="Collection.html#optional-restrictions">optional</a>) */ boolean contains(Object o); /** * Returns an iterator over the elements in this list in proper sequence. * * @return an iterator over the elements in this list in proper sequence */ Iterator<E> iterator(); /** * Returns an array containing all of the elements in this list in proper * sequence (from first to last element). * * <p>The returned array will be "safe" in that no references to it are * maintained by this list. (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. * * <p>This method acts as bridge between array-based and collection-based * APIs. * * @return an array containing all of the elements in this list in proper * sequence * @see Arrays#asList(Object[]) */ Object[] toArray(); /** * 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 is that of the specified 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. * * <p>If the list fits in the specified array with room to spare (i.e., * the array has more elements than the list), the element in the array * immediately following the end of the list is set to <tt>null</tt>. * (This is useful in determining the length of the list <i>only</i> if * the caller knows that the list does not contain any null elements.) * * <p>Like the {@link #toArray()} method, this method acts as bridge between * array-based and collection-based APIs. 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. * * <p>Suppose <tt>x</tt> is a list known to contain only strings. * The following code can be used to dump the list into a newly * allocated array of <tt>String</tt>: * * <pre>{@code * String[] y = x.toArray(new String[0]); * }</pre> * * Note that <tt>toArray(new Object[0])</tt> is identical in function to * <tt>toArray()</tt>. * * @param 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. * @return an array containing the elements of this list * @throws ArrayStoreException if the runtime type of the specified array * is not a supertype of the runtime type of every element in * this list * @throws NullPointerException if the specified array is null */ <T> T[] toArray(T[] a); // Modification Operations /** * Appends the specified element to the end of this list (optional * operation). * * <p>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. * * @param e element to be appended to this list * @return <tt>true</tt> (as specified by {@link Collection#add}) * @throws UnsupportedOperationException if the <tt>add</tt> operation * is not supported by this list * @throws ClassCastException if the class of the specified element * prevents it from being added to this list * @throws NullPointerException if the specified element is null and this * list does not permit null elements * @throws IllegalArgumentException if some property of this element * prevents it from being added to this list */ boolean add(E e); /** * Removes the first occurrence of the specified element from this list, * if it is present (optional operation). If this list does not contain * the element, it is unchanged. More formally, removes the element with * the lowest index <tt>i</tt> such that * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt> * (if such an element exists). Returns <tt>true</tt> if this list * contained the specified element (or equivalently, if this list changed * as a result of the call). * * @param o element to be removed from this list, if present * @return <tt>true</tt> if this list contained the specified element * @throws ClassCastException if the type of the specified element * is incompatible with this list * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if the specified element is null and this * list 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 list */ boolean remove(Object o); // Bulk Modification Operations /** * Returns <tt>true</tt> if this list contains all of the elements of the * specified collection. * * @param c collection to be checked for containment in this list * @return <tt>true</tt> if this list contains all of the elements of the * specified collection * @throws ClassCastException if the types of one or more elements * in the specified collection are incompatible with this * list * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if the specified collection contains one * or more null elements and this list does not permit null * elements * (<a href="Collection.html#optional-restrictions">optional</a>), * or if the specified collection is null * @see #contains(Object) */ boolean containsAll(Collection<?> c); /** * Appends all of the elements in the specified collection to the end of * this list, in the order that they are returned by the specified * collection's iterator (optional operation). 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.) * * @param c collection containing elements to be added to this list * @return <tt>true</tt> if this list changed as a result of the call * @throws UnsupportedOperationException if the <tt>addAll</tt> operation * is not supported by this list * @throws ClassCastException if the class of an element of the specified * collection prevents it from being added to this list * @throws NullPointerException if the specified collection contains one * or more null elements and this list does not permit null * elements, or if the specified collection is null * @throws IllegalArgumentException if some property of an element of the * specified collection prevents it from being added to this list * @see #add(Object) */ boolean addAll(Collection<? extends E> c); /** * Inserts all of the elements in the specified collection into this * list at the specified position (optional operation). 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 are 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.) * * @param index index at which to insert the first element from the * specified collection * @param c collection containing elements to be added to this list * @return <tt>true</tt> if this list changed as a result of the call * @throws UnsupportedOperationException if the <tt>addAll</tt> operation * is not supported by this list * @throws ClassCastException if the class of an element of the specified * collection prevents it from being added to this list * @throws NullPointerException if the specified collection contains one * or more null elements and this list does not permit null * elements, or if the specified collection is null * @throws IllegalArgumentException if some property of an element of the * specified collection prevents it from being added to this list * @throws IndexOutOfBoundsException if the index is out of range * (<tt>index < 0 || index > size()</tt>) */ boolean addAll(int index, Collection<? extends E> c); /** * Removes from this list all of its elements that are contained in the * specified collection (optional operation). * * @param c collection containing elements to be removed from this list * @return <tt>true</tt> if this list changed as a result of the call * @throws UnsupportedOperationException if the <tt>removeAll</tt> operation * is not supported by this list * @throws ClassCastException if the class of an element of this list * is incompatible with the specified collection * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if this list contains a null element and the * specified collection does not permit null elements * (<a href="Collection.html#optional-restrictions">optional</a>), * or if the specified collection is null * @see #remove(Object) * @see #contains(Object) */ boolean removeAll(Collection<?> c); /** * Retains only the elements in this list that are contained in the * specified collection (optional operation). In other words, removes * from this list all of its elements that are not contained in the * specified collection. * * @param c collection containing elements to be retained in this list * @return <tt>true</tt> if this list changed as a result of the call * @throws UnsupportedOperationException if the <tt>retainAll</tt> operation * is not supported by this list * @throws ClassCastException if the class of an element of this list * is incompatible with the specified collection * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if this list contains a null element and the * specified collection does not permit null elements * (<a href="Collection.html#optional-restrictions">optional</a>), * or if the specified collection is null * @see #remove(Object) * @see #contains(Object) */ boolean retainAll(Collection<?> c); /** * Replaces each element of this list with the result of applying the * operator to that element. Errors or runtime exceptions thrown by * the operator are relayed to the caller. * * @implSpec * The default implementation is equivalent to, for this {@code list}: * <pre>{@code * final ListIterator<E> li = list.listIterator(); * while (li.hasNext()) { * li.set(operator.apply(li.next())); * } * }</pre> * * If the list's list-iterator does not support the {@code set} operation * then an {@code UnsupportedOperationException} will be thrown when * replacing the first element. * * @param operator the operator to apply to each element * @throws UnsupportedOperationException if this list is unmodifiable. * Implementations may throw this exception if an element * cannot be replaced or if, in general, modification is not * supported * @throws NullPointerException if the specified operator is null or * if the operator result is a null value and this list does * not permit null elements * (<a href="Collection.html#optional-restrictions">optional</a>) * @since 1.8 */ default void replaceAll(UnaryOperator<E> operator) { Objects.requireNonNull(operator); final ListIterator<E> li = this.listIterator(); while (li.hasNext()) { li.set(operator.apply(li.next())); } } /** * Sorts this list according to the order induced by the specified * {@link Comparator}. * * <p>All elements in this list must be <i>mutually comparable</i> using the * specified comparator (that is, {@code c.compare(e1, e2)} must not throw * a {@code ClassCastException} for any elements {@code e1} and {@code e2} * in the list). * * <p>If the specified comparator is {@code null} then all elements in this * list must implement the {@link Comparable} interface and the elements' * {@linkplain Comparable natural ordering} should be used. * * <p>This list must be modifiable, but need not be resizable. * * @implSpec * The default implementation obtains an array containing all elements in * this list, sorts the array, and iterates over this list resetting each * element from the corresponding position in the array. (This avoids the * n<sup>2</sup> log(n) performance that would result from attempting * to sort a linked list in place.) * * @implNote * This implementation is a stable, adaptive, iterative mergesort that * requires far fewer than n lg(n) comparisons when the input array is * partially sorted, while offering the performance of a traditional * mergesort when the input array is randomly ordered. If the input array * is nearly sorted, the implementation requires approximately n * comparisons. Temporary storage requirements vary from a small constant * for nearly sorted input arrays to n/2 object references for randomly * ordered input arrays. * * <p>The implementation takes equal advantage of ascending and * descending order in its input array, and can take advantage of * ascending and descending order in different parts of the same * input array. It is well-suited to merging two or more sorted arrays: * simply concatenate the arrays and sort the resulting array. * * <p>The implementation was adapted from Tim Peters's list sort for Python * (<a href="http://svn.python.org/projects/python/trunk/Objects/listsort.txt"> * TimSort</a>). It uses techniques from Peter McIlroy's "Optimistic * Sorting and Information Theoretic Complexity", in Proceedings of the * Fourth Annual ACM-SIAM Symposium on Discrete Algorithms, pp 467-474, * January 1993. * * @param c the {@code Comparator} used to compare list elements. * A {@code null} value indicates that the elements' * {@linkplain Comparable natural ordering} should be used * @throws ClassCastException if the list contains elements that are not * <i>mutually comparable</i> using the specified comparator * @throws UnsupportedOperationException if the list's list-iterator does * not support the {@code set} operation * @throws IllegalArgumentException * (<a href="Collection.html#optional-restrictions">optional</a>) * if the comparator is found to violate the {@link Comparator} * contract * @since 1.8 */ @SuppressWarnings({"unchecked", "rawtypes"}) default void sort(Comparator<? super E> c) { Object[] a = this.toArray(); Arrays.sort(a, (Comparator) c); ListIterator<E> i = this.listIterator(); for (Object e : a) { i.next(); i.set((E) e); } } /** * Removes all of the elements from this list (optional operation). * The list will be empty after this call returns. * * @throws UnsupportedOperationException if the <tt>clear</tt> operation * is not supported by this list */ void clear(); // Comparison and hashing /** * Compares the specified object with this list for equality. Returns * <tt>true</tt> 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 <i>equal</i>. (Two elements <tt>e1</tt> and * <tt>e2</tt> are <i>equal</i> if <tt>(e1==null ? e2==null : * e1.equals(e2))</tt>.) 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 <tt>List</tt> interface. * * @param o the object to be compared for equality with this list * @return <tt>true</tt> if the specified object is equal to this list */ boolean equals(Object o); /** * Returns the hash code value for this list. The hash code of a list * is defined to be the result of the following calculation: * <pre>{@code * int hashCode = 1; * for (E e : list) * hashCode = 31*hashCode + (e==null ? 0 : e.hashCode()); * }</pre> * This ensures that <tt>list1.equals(list2)</tt> implies that * <tt>list1.hashCode()==list2.hashCode()</tt> for any two lists, * <tt>list1</tt> and <tt>list2</tt>, as required by the general * contract of {@link Object#hashCode}. * * @return the hash code value for this list * @see Object#equals(Object) * @see #equals(Object) */ int hashCode(); // Positional Access Operations /** * Returns the element at the specified position in this list. * * @param index index of the element to return * @return the element at the specified position in this list * @throws IndexOutOfBoundsException if the index is out of range * (<tt>index < 0 || index >= size()</tt>) */ E get(int index); /** * Replaces the element at the specified position in this list with the * specified element (optional operation). * * @param index index of the element to replace * @param element element to be stored at the specified position * @return the element previously at the specified position * @throws UnsupportedOperationException if the <tt>set</tt> operation * is not supported by this list * @throws ClassCastException if the class of the specified element * prevents it from being added to this list * @throws NullPointerException if the specified element is null and * this list does not permit null elements * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this list * @throws IndexOutOfBoundsException if the index is out of range * (<tt>index < 0 || index >= size()</tt>) */ E set(int index, E element); /** * Inserts the specified element at the specified position in this list * (optional operation). Shifts the element currently at that position * (if any) and any subsequent elements to the right (adds one to their * indices). * * @param index index at which the specified element is to be inserted * @param element element to be inserted * @throws UnsupportedOperationException if the <tt>add</tt> operation * is not supported by this list * @throws ClassCastException if the class of the specified element * prevents it from being added to this list * @throws NullPointerException if the specified element is null and * this list does not permit null elements * @throws IllegalArgumentException if some property of the specified * element prevents it from being added to this list * @throws IndexOutOfBoundsException if the index is out of range * (<tt>index < 0 || index > size()</tt>) */ void add(int index, E element); /** * Removes the element at the specified position in this list (optional * operation). Shifts any subsequent elements to the left (subtracts one * from their indices). Returns the element that was removed from the * list. * * @param index the index of the element to be removed * @return the element previously at the specified position * @throws UnsupportedOperationException if the <tt>remove</tt> operation * is not supported by this list * @throws IndexOutOfBoundsException if the index is out of range * (<tt>index < 0 || index >= size()</tt>) */ E remove(int index); // Search Operations /** * Returns the index of the first occurrence of the specified element * in this list, or -1 if this list does not contain the element. * More formally, returns the lowest index <tt>i</tt> such that * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, * or -1 if there is no such index. * * @param o element to search for * @return the index of the first occurrence of the specified element in * this list, or -1 if this list does not contain the element * @throws ClassCastException if the type of the specified element * is incompatible with this list * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if the specified element is null and this * list does not permit null elements * (<a href="Collection.html#optional-restrictions">optional</a>) */ int indexOf(Object o); /** * Returns the index of the last occurrence of the specified element * in this list, or -1 if this list does not contain the element. * More formally, returns the highest index <tt>i</tt> such that * <tt>(o==null ? get(i)==null : o.equals(get(i)))</tt>, * or -1 if there is no such index. * * @param o element to search for * @return the index of the last occurrence of the specified element in * this list, or -1 if this list does not contain the element * @throws ClassCastException if the type of the specified element * is incompatible with this list * (<a href="Collection.html#optional-restrictions">optional</a>) * @throws NullPointerException if the specified element is null and this * list does not permit null elements * (<a href="Collection.html#optional-restrictions">optional</a>) */ int lastIndexOf(Object o); // List Iterators /** * Returns a list iterator over the elements in this list (in proper * sequence). * * @return a list iterator over the elements in this list (in proper * sequence) */ ListIterator<E> listIterator(); /** * Returns a list iterator over the elements in this list (in proper * sequence), starting at the specified position in the list. * The specified index indicates the first element that would be * returned by an initial call to {@link ListIterator#next next}. * An initial call to {@link ListIterator#previous previous} would * return the element with the specified index minus one. * * @param index index of the first element to be returned from the * list iterator (by a call to {@link ListIterator#next next}) * @return a list iterator over the elements in this list (in proper * sequence), starting at the specified position in the list * @throws IndexOutOfBoundsException if the index is out of range * ({@code index < 0 || index > size()}) */ ListIterator<E> listIterator(int index); // View /** * Returns a view of the portion of this list between the specified * <tt>fromIndex</tt>, inclusive, and <tt>toIndex</tt>, exclusive. (If * <tt>fromIndex</tt> and <tt>toIndex</tt> 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.<p> * * 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: * <pre>{@code * list.subList(from, to).clear(); * }</pre> * Similar idioms may be constructed for <tt>indexOf</tt> and * <tt>lastIndexOf</tt>, and all of the algorithms in the * <tt>Collections</tt> class can be applied to a subList.<p> * * The semantics of the list returned by this method become undefined if * the backing list (i.e., this list) is <i>structurally modified</i> in * any way other than via the returned list. (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.) * * @param fromIndex low endpoint (inclusive) of the subList * @param toIndex high endpoint (exclusive) of the subList * @return a view of the specified range within this list * @throws IndexOutOfBoundsException for an illegal endpoint index value * (<tt>fromIndex < 0 || toIndex > size || * fromIndex > toIndex</tt>) */ List<E> subList(int fromIndex, int toIndex); /** * Creates a {@link Spliterator} over the elements in this list. * * <p>The {@code Spliterator} reports {@link Spliterator#SIZED} and * {@link Spliterator#ORDERED}. Implementations should document the * reporting of additional characteristic values. * * @implSpec * The default implementation creates a * <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator * from the list's {@code Iterator}. The spliterator inherits the * <em>fail-fast</em> properties of the list's iterator. * * @implNote * The created {@code Spliterator} additionally reports * {@link Spliterator#SUBSIZED}. * * @return a {@code Spliterator} over the elements in this list * @since 1.8 */ @Override default Spliterator<E> spliterator() { return Spliterators.spliterator(this, Spliterator.ORDERED); } }
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作者：ylbtech 出处：http://ylbtech.cnblogs.com/ 本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利。 |