Java Collection接口

如下为Collection接口中部分函数：

public interface Collection<E> extends Iterable<E> {// Query Operationsint size();boolean isEmpty();boolean contains(Object o);Iterator<E> iterator();<T> T[] toArray(T[] a);boolean add(E e);boolean remove(Object o);boolean containsAll(Collection<?> c);boolean addAll(Collection<? extends E> c);boolean removeAll(Collection<?> c);boolean retainAll(Collection<?> c);void clear();
}

都是集合类中一些共有的函数定义。

以下为Collection.java源码：

/** Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.*********************/package java.util;import java.util.function.Predicate;
import java.util.stream.Stream;
import java.util.stream.StreamSupport;/*** The root interface in the <i>collection hierarchy</i>.  A collection* represents a group of objects, known as its <i>elements</i>.  Some* collections allow duplicate elements and others do not.  Some are ordered* and others unordered.  The JDK does not provide any <i>direct</i>* implementations of this interface: it provides implementations of more* specific subinterfaces like <tt>Set</tt> and <tt>List</tt>.  This interface* is typically used to pass collections around and manipulate them where* maximum generality is desired.** <p><i>Bags</i> or <i>multisets</i> (unordered collections that may contain* duplicate elements) should implement this interface directly.** <p>All general-purpose <tt>Collection</tt> implementation classes (which* typically implement <tt>Collection</tt> indirectly through one of its* subinterfaces) should provide two "standard" constructors: a void (no* arguments) constructor, which creates an empty collection, and a* constructor with a single argument of type <tt>Collection</tt>, which* creates a new collection with the same elements as its argument.  In* effect, the latter constructor allows the user to copy any collection,* producing an equivalent collection of the desired implementation type.* There is no way to enforce this convention (as interfaces cannot contain* constructors) but all of the general-purpose <tt>Collection</tt>* implementations in the Java platform libraries comply.** <p>The "destructive" methods contained in this interface, that is, the* methods that modify the collection on which they operate, are specified to* throw <tt>UnsupportedOperationException</tt> if this collection does not* support the operation.  If this is the case, these methods may, but are not* required to, throw an <tt>UnsupportedOperationException</tt> if the* invocation would have no effect on the collection.  For example, invoking* the {@link #addAll(Collection)} method on an unmodifiable collection may,* but is not required to, throw the exception if the collection to be added* is empty.** <p><a name="optional-restrictions">* Some collection implementations have restrictions on the elements that* they may contain.</a>  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 collection 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>It is up to each collection to determine its own synchronization* policy.  In the absence of a stronger guarantee by the* implementation, undefined behavior may result from the invocation* of any method on a collection that is being mutated by another* thread; this includes direct invocations, passing the collection to* a method that might perform invocations, and using an existing* iterator to examine the collection.** <p>Many methods in Collections Framework interfaces are defined in* terms of the {@link Object#equals(Object) equals} method.  For example,* the specification for the {@link #contains(Object) contains(Object o)}* method says: "returns <tt>true</tt> if and only if this collection* contains at least one element <tt>e</tt> such that* <tt>(o==null ? e==null : o.equals(e))</tt>."  This specification should* <i>not</i> be construed to imply that invoking <tt>Collection.contains</tt>* with a non-null argument <tt>o</tt> will cause <tt>o.equals(e)</tt> to be* invoked for any element <tt>e</tt>.  Implementations are free to implement* optimizations whereby the <tt>equals</tt> invocation is avoided, for* example, by first comparing the hash codes of the two elements.  (The* {@link Object#hashCode()} specification guarantees that two objects with* unequal hash codes cannot be equal.)  More generally, implementations of* the various Collections Framework interfaces are free to take advantage of* the specified behavior of underlying {@link Object} methods wherever the* implementor deems it appropriate.** <p>Some collection operations which perform recursive traversal of the* collection may fail with an exception for self-referential instances where* the collection directly or indirectly contains itself. This includes the* {@code clone()}, {@code equals()}, {@code hashCode()} and {@code toString()}* methods. Implementations may optionally handle the self-referential scenario,* however most current implementations do not do so.** <p>This interface is a member of the* <a href="{@docRoot}/../technotes/guides/collections/index.html">* Java Collections Framework</a>.** @implSpec* The default method implementations (inherited or otherwise) do not apply any* synchronization protocol.  If a {@code Collection} implementation has a* specific synchronization protocol, then it must override default* implementations to apply that protocol.** @param <E> the type of elements in this collection** @author  Josh Bloch* @author  Neal Gafter* @see     Set* @see     List* @see     Map* @see     SortedSet* @see     SortedMap* @see     HashSet* @see     TreeSet* @see     ArrayList* @see     LinkedList* @see     Vector* @see     Collections* @see     Arrays* @see     AbstractCollection* @since 1.2*/public interface Collection<E> extends Iterable<E> {// Query Operations/*** Returns the number of elements in this collection.  If this collection* contains more than <tt>Integer.MAX_VALUE</tt> elements, returns* <tt>Integer.MAX_VALUE</tt>.** @return the number of elements in this collection*/int size();/*** Returns <tt>true</tt> if this collection contains no elements.** @return <tt>true</tt> if this collection contains no elements*/boolean isEmpty();/*** Returns <tt>true</tt> if this collection contains the specified element.* More formally, returns <tt>true</tt> if and only if this collection* 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 collection is to be tested* @return <tt>true</tt> if this collection contains the specified*         element* @throws ClassCastException if the type of the specified element*         is incompatible with this collection*         (<a href="#optional-restrictions">optional</a>)* @throws NullPointerException if the specified element is null and this*         collection does not permit null elements*         (<a href="#optional-restrictions">optional</a>)*/boolean contains(Object o);/*** Returns an iterator over the elements in this collection.  There are no* guarantees concerning the order in which the elements are returned* (unless this collection is an instance of some class that provides a* guarantee).** @return an <tt>Iterator</tt> over the elements in this collection*/Iterator<E> iterator();/*** Returns an array containing all of the elements in this collection.* If this collection makes any guarantees as to what order its elements* are returned by its iterator, this method must return the elements in* the same order.** <p>The returned array will be "safe" in that no references to it are* maintained by this collection.  (In other words, this method must* allocate a new array even if this collection 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 collection*/Object[] toArray();/*** Returns an array containing all of the elements in this collection;* the runtime type of the returned array is that of the specified array.* If the collection 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 collection.** <p>If this collection fits in the specified array with room to spare* (i.e., the array has more elements than this collection), the element* in the array immediately following the end of the collection is set to* <tt>null</tt>.  (This is useful in determining the length of this* collection <i>only</i> if the caller knows that this collection does* not contain any <tt>null</tt> elements.)** <p>If this collection makes any guarantees as to what order its elements* are returned by its iterator, this method must return the elements in* the same order.** <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 collection known to contain only strings.* The following code can be used to dump the collection into a newly* allocated array of <tt>String</tt>:** <pre>*     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 <T> the runtime type of the array to contain the collection* @param a the array into which the elements of this collection 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 all of the elements in this collection* @throws ArrayStoreException if the runtime type of the specified array*         is not a supertype of the runtime type of every element in*         this collection* @throws NullPointerException if the specified array is null*/<T> T[] toArray(T[] a);// Modification Operations/*** Ensures that this collection contains the specified element (optional* operation).  Returns <tt>true</tt> if this collection changed as a* result of the call.  (Returns <tt>false</tt> if this collection does* not permit duplicates and already contains the specified element.)<p>** Collections that support this operation may place limitations on what* elements may be added to this collection.  In particular, some* collections will refuse to add <tt>null</tt> elements, and others will* impose restrictions on the type of elements that may be added.* Collection classes should clearly specify in their documentation any* restrictions on what elements may be added.<p>** If a collection refuses to add a particular element for any reason* other than that it already contains the element, it <i>must</i> throw* an exception (rather than returning <tt>false</tt>).  This preserves* the invariant that a collection always contains the specified element* after this call returns.** @param e element whose presence in this collection is to be ensured* @return <tt>true</tt> if this collection changed as a result of the*         call* @throws UnsupportedOperationException if the <tt>add</tt> operation*         is not supported by this collection* @throws ClassCastException if the class of the specified element*         prevents it from being added to this collection* @throws NullPointerException if the specified element is null and this*         collection does not permit null elements* @throws IllegalArgumentException if some property of the element*         prevents it from being added to this collection* @throws IllegalStateException if the element cannot be added at this*         time due to insertion restrictions*/boolean add(E e);/*** Removes a single instance of the specified element from this* collection, if it is present (optional operation).  More formally,* removes an element <tt>e</tt> such that* <tt>(o==null ? e==null : o.equals(e))</tt>, if* this collection contains one or more such elements.  Returns* <tt>true</tt> if this collection contained the specified element (or* equivalently, if this collection changed as a result of the call).** @param o element to be removed from this collection, if present* @return <tt>true</tt> if an element was removed as a result of this call* @throws ClassCastException if the type of the specified element*         is incompatible with this collection*         (<a href="#optional-restrictions">optional</a>)* @throws NullPointerException if the specified element is null and this*         collection does not permit null elements*         (<a href="#optional-restrictions">optional</a>)* @throws UnsupportedOperationException if the <tt>remove</tt> operation*         is not supported by this collection*/boolean remove(Object o);// Bulk Operations/*** Returns <tt>true</tt> if this collection contains all of the elements* in the specified collection.** @param  c collection to be checked for containment in this collection* @return <tt>true</tt> if this collection contains all of the elements*         in the specified collection* @throws ClassCastException if the types of one or more elements*         in the specified collection are incompatible with this*         collection*         (<a href="#optional-restrictions">optional</a>)* @throws NullPointerException if the specified collection contains one*         or more null elements and this collection does not permit null*         elements*         (<a href="#optional-restrictions">optional</a>),*         or if the specified collection is null.* @see    #contains(Object)*/boolean containsAll(Collection<?> c);/*** Adds all of the elements in the specified collection to this collection* (optional operation).  The behavior of this operation is undefined if* the specified collection is modified while the operation is in progress.* (This implies that the behavior of this call is undefined if the* specified collection is this collection, and this collection is* nonempty.)** @param c collection containing elements to be added to this collection* @return <tt>true</tt> if this collection changed as a result of the call* @throws UnsupportedOperationException if the <tt>addAll</tt> operation*         is not supported by this collection* @throws ClassCastException if the class of an element of the specified*         collection prevents it from being added to this collection* @throws NullPointerException if the specified collection contains a*         null element and this collection 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*         collection* @throws IllegalStateException if not all the elements can be added at*         this time due to insertion restrictions* @see #add(Object)*/boolean addAll(Collection<? extends E> c);/*** Removes all of this collection's elements that are also contained in the* specified collection (optional operation).  After this call returns,* this collection will contain no elements in common with the specified* collection.** @param c collection containing elements to be removed from this collection* @return <tt>true</tt> if this collection changed as a result of the*         call* @throws UnsupportedOperationException if the <tt>removeAll</tt> method*         is not supported by this collection* @throws ClassCastException if the types of one or more elements*         in this collection are incompatible with the specified*         collection*         (<a href="#optional-restrictions">optional</a>)* @throws NullPointerException if this collection contains one or more*         null elements and the specified collection does not support*         null elements*         (<a href="#optional-restrictions">optional</a>),*         or if the specified collection is null* @see #remove(Object)* @see #contains(Object)*/boolean removeAll(Collection<?> c);/*** Removes all of the elements of this collection that satisfy the given* predicate.  Errors or runtime exceptions thrown during iteration or by* the predicate are relayed to the caller.** @implSpec* The default implementation traverses all elements of the collection using* its {@link #iterator}.  Each matching element is removed using* {@link Iterator#remove()}.  If the collection's iterator does not* support removal then an {@code UnsupportedOperationException} will be* thrown on the first matching element.** @param filter a predicate which returns {@code true} for elements to be*        removed* @return {@code true} if any elements were removed* @throws NullPointerException if the specified filter is null* @throws UnsupportedOperationException if elements cannot be removed*         from this collection.  Implementations may throw this exception if a*         matching element cannot be removed or if, in general, removal is not*         supported.* @since 1.8*/default boolean removeIf(Predicate<? super E> filter) {Objects.requireNonNull(filter);boolean removed = false;final Iterator<E> each = iterator();while (each.hasNext()) {if (filter.test(each.next())) {each.remove();removed = true;}}return removed;}/*** Retains only the elements in this collection that are contained in the* specified collection (optional operation).  In other words, removes from* this collection all of its elements that are not contained in the* specified collection.** @param c collection containing elements to be retained in this collection* @return <tt>true</tt> if this collection changed as a result of the call* @throws UnsupportedOperationException if the <tt>retainAll</tt> operation*         is not supported by this collection* @throws ClassCastException if the types of one or more elements*         in this collection are incompatible with the specified*         collection*         (<a href="#optional-restrictions">optional</a>)* @throws NullPointerException if this collection contains one or more*         null elements and the specified collection does not permit null*         elements*         (<a href="#optional-restrictions">optional</a>),*         or if the specified collection is null* @see #remove(Object)* @see #contains(Object)*/boolean retainAll(Collection<?> c);/*** Removes all of the elements from this collection (optional operation).* The collection will be empty after this method returns.** @throws UnsupportedOperationException if the <tt>clear</tt> operation*         is not supported by this collection*/void clear();// Comparison and hashing/*** Compares the specified object with this collection for equality. <p>** While the <tt>Collection</tt> interface adds no stipulations to the* general contract for the <tt>Object.equals</tt>, programmers who* implement the <tt>Collection</tt> interface "directly" (in other words,* create a class that is a <tt>Collection</tt> but is not a <tt>Set</tt>* or a <tt>List</tt>) must exercise care if they choose to override the* <tt>Object.equals</tt>.  It is not necessary to do so, and the simplest* course of action is to rely on <tt>Object</tt>'s implementation, but* the implementor may wish to implement a "value comparison" in place of* the default "reference comparison."  (The <tt>List</tt> and* <tt>Set</tt> interfaces mandate such value comparisons.)<p>** The general contract for the <tt>Object.equals</tt> method states that* equals must be symmetric (in other words, <tt>a.equals(b)</tt> if and* only if <tt>b.equals(a)</tt>).  The contracts for <tt>List.equals</tt>* and <tt>Set.equals</tt> state that lists are only equal to other lists,* and sets to other sets.  Thus, a custom <tt>equals</tt> method for a* collection class that implements neither the <tt>List</tt> nor* <tt>Set</tt> interface must return <tt>false</tt> when this collection* is compared to any list or set.  (By the same logic, it is not possible* to write a class that correctly implements both the <tt>Set</tt> and* <tt>List</tt> interfaces.)** @param o object to be compared for equality with this collection* @return <tt>true</tt> if the specified object is equal to this* collection** @see Object#equals(Object)* @see Set#equals(Object)* @see List#equals(Object)*/boolean equals(Object o);/*** Returns the hash code value for this collection.  While the* <tt>Collection</tt> interface adds no stipulations to the general* contract for the <tt>Object.hashCode</tt> method, programmers should* take note that any class that overrides the <tt>Object.equals</tt>* method must also override the <tt>Object.hashCode</tt> method in order* to satisfy the general contract for the <tt>Object.hashCode</tt> method.* In particular, <tt>c1.equals(c2)</tt> implies that* <tt>c1.hashCode()==c2.hashCode()</tt>.** @return the hash code value for this collection** @see Object#hashCode()* @see Object#equals(Object)*/int hashCode();/*** Creates a {@link Spliterator} over the elements in this collection.** Implementations should document characteristic values reported by the* spliterator.  Such characteristic values are not required to be reported* if the spliterator reports {@link Spliterator#SIZED} and this collection* contains no elements.** <p>The default implementation should be overridden by subclasses that* can return a more efficient spliterator.  In order to* preserve expected laziness behavior for the {@link #stream()} and* {@link #parallelStream()}} methods, spliterators should either have the* characteristic of {@code IMMUTABLE} or {@code CONCURRENT}, or be* <em><a href="Spliterator.html#binding">late-binding</a></em>.* If none of these is practical, the overriding class should describe the* spliterator's documented policy of binding and structural interference,* and should override the {@link #stream()} and {@link #parallelStream()}* methods to create streams using a {@code Supplier} of the spliterator,* as in:* <pre>{@code*     Stream<E> s = StreamSupport.stream(() -> spliterator(), spliteratorCharacteristics)* }</pre>* <p>These requirements ensure that streams produced by the* {@link #stream()} and {@link #parallelStream()} methods will reflect the* contents of the collection as of initiation of the terminal stream* operation.** @implSpec* The default implementation creates a* <em><a href="Spliterator.html#binding">late-binding</a></em> spliterator* from the collections's {@code Iterator}.  The spliterator inherits the* <em>fail-fast</em> properties of the collection's iterator.* <p>* The created {@code Spliterator} reports {@link Spliterator#SIZED}.** @implNote* The created {@code Spliterator} additionally reports* {@link Spliterator#SUBSIZED}.** <p>If a spliterator covers no elements then the reporting of additional* characteristic values, beyond that of {@code SIZED} and {@code SUBSIZED},* does not aid clients to control, specialize or simplify computation.* However, this does enable shared use of an immutable and empty* spliterator instance (see {@link Spliterators#emptySpliterator()}) for* empty collections, and enables clients to determine if such a spliterator* covers no elements.** @return a {@code Spliterator} over the elements in this collection* @since 1.8*/@Overridedefault Spliterator<E> spliterator() {return Spliterators.spliterator(this, 0);}/*** Returns a sequential {@code Stream} with this collection as its source.** <p>This method should be overridden when the {@link #spliterator()}* method cannot return a spliterator that is {@code IMMUTABLE},* {@code CONCURRENT}, or <em>late-binding</em>. (See {@link #spliterator()}* for details.)** @implSpec* The default implementation creates a sequential {@code Stream} from the* collection's {@code Spliterator}.** @return a sequential {@code Stream} over the elements in this collection* @since 1.8*/default Stream<E> stream() {return StreamSupport.stream(spliterator(), false);}/*** Returns a possibly parallel {@code Stream} with this collection as its* source.  It is allowable for this method to return a sequential stream.** <p>This method should be overridden when the {@link #spliterator()}* method cannot return a spliterator that is {@code IMMUTABLE},* {@code CONCURRENT}, or <em>late-binding</em>. (See {@link #spliterator()}* for details.)** @implSpec* The default implementation creates a parallel {@code Stream} from the* collection's {@code Spliterator}.** @return a possibly parallel {@code Stream} over the elements in this* collection* @since 1.8*/default Stream<E> parallelStream() {return StreamSupport.stream(spliterator(), true);}
}

Java Collection接口相关推荐

Java Collection接口详解
Collection 接口是 List.Set 和 Queue 接口的父接口,通常情况下不被直接使用.Collection 接口定义了一些通用的方法,通过这些方法可以实现对集合的基本操作.定义的方法既 ...
java 集合接口_Java集合之Collection接口
1 - Java集合介绍 /* 1. 一方面, 面向对象语言对事物的体现都是以对象的形式,为了方便对多个对象的操作,就要对对象进行存储. 2. 另一方面,使用Array存储对象方面具有一些弊端,而 ...
Java集合框架系列教程三：Collection接口
翻译自:The Collection Interface 一个集合表示一组对象.Collection接口被用来传递对象的集合,具有最强的通用性.例如,默认所有的集合实现都有一个构造器带有一个Colle ...
java list接口为何要重新声明collection接口的方法_JAVA Collection接口中List Map 和Set的区别（转）...
Java中的集合包括三大类,它们是Set(集).List(列表)和Map(映射),它们都处于java.util包中,Set.List和Map都是接口,它们有各自的实现类.Set的实现类主要有HashS ...
java之集合框架一Collection接口
1.集合的由来: 我们学习的是面向对象的语言.而面向对象语言对事物的描述是通过对象体现的.为了方便对多个对象进行操作,我们就必须把多个对象进行存储.而要想存储多个对象,就不能是一个基本的变量,而应该是 ...
Java™ 教程（Collection接口）
Collection接口 Collection表示一组称为其元素的对象,Collection接口用于传递需要最大通用性的对象集合,例如,按照惯例,所有通用集合实现都有一个带有Collection参数的 ...
java的知识点23——泛型Generics、Collection接口、List特点和常用方法、 ArrayList特点和底层实现
泛型Generics 一般通过"容器"来容纳和管理数据.程序中的"容器"就是用来容纳和管理数据. 数组就是一种容器,可以在其中放置对象或基本类型数据. 数组的优 ...
Java学习之容器上（Collection接口常用方法,Iterator接口,使用foreach循环遍历Collection集合元素,Set集合通用知识(Hashset类,hashcode()与Lin
1.容器API的类图结构如下: JAVA的集合类是一种特别有用的工具类,它可以用于存储数量不等的多个对象,并可以实现常用数据结构,如栈,队列等,除此之外,JAVA集合还可用于保存具有映射关系的关联数组 ...
9.1-全栈Java笔记: 容器泛型—认识Collection接口
开发和学习中需要时刻和数据打交道,如果组织这些数据是我们编程中重要的内容. 我们一般通过"容器"来容纳和管理数据. 事实上,数组就是一种容器,可以在其中放置对象或基本类型数据. ...

Java Collection接口

Java Collection接口相关推荐

最新文章

热门文章