Set 接口 源代码


Set 接口 源代码

/*
 * Copyright (c) 1997, 2013, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 *
 */

package java.util;

/**
 * A collection that contains no duplicate elements.  More formally, sets
 * contain no pair of elements e1 and e2 such that
 * e1.equals(e2), and at most one null element.  As implied by
 * its name, this interface models the mathematical set abstraction.
 *
 * set不包含重复元素,不存在e1.equals(e2),set最多有一个null值
 *
 * 

The Set interface places additional stipulations, beyond those * inherited from the Collection interface, on the contracts of all * constructors and on the contracts of the add, equals and * hashCode methods. Declarations for other inherited methods are * also included here for convenience. (The specifications accompanying these * declarations have been tailored to the Set interface, but they do * not contain any additional stipulations.) * *

The additional stipulation on constructors is, not surprisingly, * that all constructors must create a set that contains no duplicate elements * (as defined above). * *

Note: Great care must be exercised if mutable objects are used as set * elements. The behavior of a set is not specified if the value of an object * is changed in a manner that affects equals comparisons while the * object is an element in the set. A special case of this prohibition is * that it is not permissible for a set to contain itself as an element. * *

Some set 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 set 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. * *

This interface is a member of the * * Java Collections Framework. * * @param the type of elements maintained by this set * * @author Josh Bloch * @author Neal Gafter * @see Collection * @see List * @see SortedSet * @see HashSet * @see TreeSet * @see AbstractSet * @see Collections#singleton(java.lang.Object) * @see Collections#EMPTY_SET * @since 1.2 */ /* 一个不包含重复元素的 collection。更确切地讲,set 不包含满足 e1.equals(e2) 的元素对 e1 和 e2, 并且最多包含一个 null 元素。正如其名称所暗示的,此接口模仿了数学上的 set 抽象。 在所有构造方法以及 add、equals 和 hashCode 方法的协定上,Set 接口还加入了其他规定, 这些规定超出了从 Collection 接口所继承的内容。出于方便考虑,它还包括了其他继承方法的声明 (这些声明的规范已经专门针对 Set 接口进行了修改,但是没有包含任何其他的规定)。 对这些构造方法的其他规定是(不要奇怪),所有构造方法必须创建一个不包含重复元素的 set(正如上面所定义的)。 注:如果将可变对象用作 set 元素,那么必须极其小心。如果对象是 set 中某个元素, 以一种影响 equals 比较的方式改变对象的值,那么 set 的行为就是不确定的。此项禁止的 一个特殊情况是不允许某个 set 包含其自身作为元素。 某些 set 实现对其所包含的元素有所限制。例如,某些实现禁止 null 元素,而某些则对 其元素的类型所有限制。试图添加不合格的元素会抛出未经检查的异常,通常是 NullPointerException 或 ClassCastException。试图查询不合格的元素是否存在可能会抛出异常,也可能简单地返回 false; 某些实现会采用前一种行为,而某些则采用后者。概括地说,试图对不合格元素执行操作时, 如果完成该操作后不会导致在 set 中插入不合格的元素,则该操作可能抛出一个异常,也可能成功, 这取决于实现的选择。此接口的规范中将这样的异常标记为“可选”。 */ public interface Set extends Collection { // Query Operations /** * Returns the number of elements in this set (its cardinality). If this * set contains more than Integer.MAX_VALUE elements, returns * Integer.MAX_VALUE. * * @return the number of elements in this set (its cardinality) */ //返回容量,最大为Integer.MAX_VALUE int size(); /** * Returns true if this set contains no elements. * * @return true if this set contains no elements */ //是否没有元素 boolean isEmpty(); /** * Returns true if this set contains the specified element. * More formally, returns true if and only if this set * contains an element e such that * (o==null ? e==null : o.equals(e)). * * @param o element whose presence in this set is to be tested * @return true if this set contains the specified element * @throws ClassCastException if the type of the specified element * is incompatible with this set * (optional) * @throws NullPointerException if the specified element is null and this * set does not permit null elements * (optional) */ //判断是否包含元素o return o==null ? e==null : o.equals(e) boolean contains(Object o); /** * Returns an iterator over the elements in this set. The elements are * returned in no particular order (unless this set is an instance of some * class that provides a guarantee). * * @return an iterator over the elements in this set */ //返回容器的迭代器 Iterator iterator(); /** * Returns an array containing all of the elements in this set. * If this set makes any guarantees as to what order its elements * are returned by its iterator, this method must return the * elements in the same order. * *

The returned array will be "safe" in that no references to it * are maintained by this set. (In other words, this method must * allocate a new array even if this set is backed by an array). * The caller is thus free to modify the returned array. * *

This method acts as bridge between array-based and collection-based * APIs. * * @return an array containing all the elements in this set */ //返回包含容器所有元素的数组 Object[] toArray(); /** * Returns an array containing all of the elements in this set; the * runtime type of the returned array is that of the specified array. * If the set 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 set. * *

If this set fits in the specified array with room to spare * (i.e., the array has more elements than this set), the element in * the array immediately following the end of the set is set to * null. (This is useful in determining the length of this * set only if the caller knows that this set does not contain * any null elements.) * *

If this set makes any guarantees as to what order its elements * are returned by its iterator, this method must return the elements * in the same order. * *

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. * *

Suppose x is a set known to contain only strings. * The following code can be used to dump the set into a newly allocated * array of String: * *

     *     String[] y = x.toArray(new String[0]);
* * Note that toArray(new Object[0]) is identical in function to * toArray(). * * @param a the array into which the elements of this set 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 the elements in this set * @throws ArrayStoreException if the runtime type of the specified array * is not a supertype of the runtime type of every element in this * set * @throws NullPointerException if the specified array is null */ //返回T类的数组 T[] toArray(T[] a); // Modification Operations /** * Adds the specified element to this set if it is not already present * (optional operation). More formally, adds the specified element * e to this set if the set contains no element e2 * such that * (e==null ? e2==null : e.equals(e2)). * If this set already contains the element, the call leaves the set * unchanged and returns false. In combination with the * restriction on constructors, this ensures that sets never contain * duplicate elements. * *

The stipulation above does not imply that sets must accept all * elements; sets may refuse to add any particular element, including * null, and throw an exception, as described in the * specification for {@link Collection#add Collection.add}. * Individual set implementations should clearly document any * restrictions on the elements that they may contain. * * @param e element to be added to this set * @return true if this set did not already contain the specified * element * @throws UnsupportedOperationException if the add operation * is not supported by this set * @throws ClassCastException if the class of the specified element * prevents it from being added to this set * @throws NullPointerException if the specified element is null and this * set does not permit null elements * @throws IllegalArgumentException if some property of the specified element * prevents it from being added to this set */ //添加元素e boolean add(E e); /** * Removes the specified element from this set if it is present * (optional operation). More formally, removes an element e * such that * (o==null ? e==null : o.equals(e)), if * this set contains such an element. Returns true if this set * contained the element (or equivalently, if this set changed as a * result of the call). (This set will not contain the element once the * call returns.) * * @param o object to be removed from this set, if present * @return true if this set contained the specified element * @throws ClassCastException if the type of the specified element * is incompatible with this set * (optional) * @throws NullPointerException if the specified element is null and this * set does not permit null elements * (optional) * @throws UnsupportedOperationException if the remove operation * is not supported by this set */ //移除掉容器中的o元素 boolean remove(Object o); // Bulk Operations /** * Returns true if this set contains all of the elements of the * specified collection. If the specified collection is also a set, this * method returns true if it is a subset of this set. * * @param c collection to be checked for containment in this set * @return true if this set 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 * set * (optional) * @throws NullPointerException if the specified collection contains one * or more null elements and this set does not permit null * elements * (optional), * or if the specified collection is null * @see #contains(Object) */ //判断容器是否包含所有c中的元素 boolean containsAll(Collection c); /** * Adds all of the elements in the specified collection to this set if * they're not already present (optional operation). If the specified * collection is also a set, the addAll operation effectively * modifies this set so that its value is the union of the two * sets. The behavior of this operation is undefined if the specified * collection is modified while the operation is in progress. * * @param c collection containing elements to be added to this set * @return true if this set changed as a result of the call * * @throws UnsupportedOperationException if the addAll operation * is not supported by this set * @throws ClassCastException if the class of an element of the * specified collection prevents it from being added to this set * @throws NullPointerException if the specified collection contains one * or more null elements and this set 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 set * @see #add(Object) */ //将c中所有元素添加到容器中 boolean addAll(Collection c); /** * Retains only the elements in this set that are contained in the * specified collection (optional operation). In other words, removes * from this set all of its elements that are not contained in the * specified collection. If the specified collection is also a set, this * operation effectively modifies this set so that its value is the * intersection of the two sets. * * @param c collection containing elements to be retained in this set * @return true if this set changed as a result of the call * @throws UnsupportedOperationException if the retainAll operation * is not supported by this set * @throws ClassCastException if the class of an element of this set * is incompatible with the specified collection * (optional) * @throws NullPointerException if this set contains a null element and the * specified collection does not permit null elements * (optional), * or if the specified collection is null * @see #remove(Object) */ //将本容器和c容器取交集 boolean retainAll(Collection c); /** * Removes from this set all of its elements that are contained in the * specified collection (optional operation). If the specified * collection is also a set, this operation effectively modifies this * set so that its value is the asymmetric set difference of * the two sets. * * @param c collection containing elements to be removed from this set * @return true if this set changed as a result of the call * @throws UnsupportedOperationException if the removeAll operation * is not supported by this set * @throws ClassCastException if the class of an element of this set * is incompatible with the specified collection * (optional) * @throws NullPointerException if this set contains a null element and the * specified collection does not permit null elements * (optional), * or if the specified collection is null * @see #remove(Object) * @see #contains(Object) */ //移除所有在容器c中出现的元素 boolean removeAll(Collection c); /** * Removes all of the elements from this set (optional operation). * The set will be empty after this call returns. * * @throws UnsupportedOperationException if the clear method * is not supported by this set */ //清除掉容器中的元素 void clear(); // Comparison and hashing /** * Compares the specified object with this set for equality. Returns * true if the specified object is also a set, the two sets * have the same size, and every member of the specified set is * contained in this set (or equivalently, every member of this set is * contained in the specified set). This definition ensures that the * equals method works properly across different implementations of the * set interface. * * @param o object to be compared for equality with this set * @return true if the specified object is equal to this set */ //元素与o是否相等 boolean equals(Object o); /** * Returns the hash code value for this set. The hash code of a set is * defined to be the sum of the hash codes of the elements in the set, * where the hash code of a null element is defined to be zero. * This ensures that s1.equals(s2) implies that * s1.hashCode()==s2.hashCode() for any two sets s1 * and s2, as required by the general contract of * {@link Object#hashCode}. * * @return the hash code value for this set * @see Object#equals(Object) * @see Set#equals(Object) */ //计算hash值 s1.hashCode() == s2.hashCode() 说明 s1.equals(s2) int hashCode(); /** * Creates a {@code Spliterator} over the elements in this set. * *

The {@code Spliterator} reports {@link Spliterator#DISTINCT}. * Implementations should document the reporting of additional * characteristic values. * * @implSpec * The default implementation creates a * late-binding spliterator * from the set's {@code Iterator}. The spliterator inherits the * fail-fast properties of the set's iterator. *

* The created {@code Spliterator} additionally reports * {@link Spliterator#SIZED}. * * @implNote * The created {@code Spliterator} additionally reports * {@link Spliterator#SUBSIZED}. * * @return a {@code Spliterator} over the elements in this set * @since 1.8 */ @Override default Spliterator spliterator() { return Spliterators.spliterator(this, Spliterator.DISTINCT); } }



你可能感兴趣的:(Java源代码,Set,源代码,Java)