--- jsr166/src/main/java/util/Queue.java 2005/07/18 01:04:11 1.32 +++ jsr166/src/main/java/util/Queue.java 2016/07/08 20:02:54 1.44 @@ -1,7 +1,7 @@ /* * Written by Doug Lea with assistance from members of JCP JSR-166 * Expert Group and released to the public domain, as explained at - * http://creativecommons.org/licenses/publicdomain + * http://creativecommons.org/publicdomain/zero/1.0/ */ package java.util; @@ -12,14 +12,14 @@ package java.util; * queues provide additional insertion, extraction, and inspection * operations. Each of these methods exists in two forms: one throws * an exception if the operation fails, the other returns a special - * value (either null or false, depending on the + * value (either {@code null} or {@code false}, depending on the * operation). The latter form of the insert operation is designed - * specifically for use with capacity-restricted Queue + * specifically for use with capacity-restricted {@code Queue} * implementations; in most implementations, insert operations cannot * fail. * - *

* + * * * * @@ -27,18 +27,18 @@ package java.util; * * * - * - * + * + * * * * - * - * + * + * * * * - * - * + * + * * *
Summary of Queue methods
Throws exception
Insert{@link #add add(e)}{@link #offer offer(e)}{@link Queue#add add(e)}{@link Queue#offer offer(e)}
Remove{@link #remove remove()}{@link #poll poll()}{@link Queue#remove remove()}{@link Queue#poll poll()}
Examine{@link #element element()}{@link #peek peek()}{@link Queue#element element()}{@link Queue#peek peek()}
* @@ -50,15 +50,15 @@ package java.util; * Whatever the ordering used, the head of the queue is that * element which would be removed by a call to {@link #remove() } or * {@link #poll()}. In a FIFO queue, all new elements are inserted at - * the tail of the queue. Other kinds of queues may use - * different placement rules. Every Queue implementation + * the tail of the queue. Other kinds of queues may use + * different placement rules. Every {@code Queue} implementation * must specify its ordering properties. * *

The {@link #offer offer} method inserts an element if possible, - * otherwise returning false. This differs from the {@link + * otherwise returning {@code false}. This differs from the {@link * java.util.Collection#add Collection.add} method, which can fail to * add an element only by throwing an unchecked exception. The - * offer method is designed for use when failure is a normal, + * {@code offer} method is designed for use when failure is a normal, * rather than exceptional occurrence, for example, in fixed-capacity * (or "bounded") queues. * @@ -66,67 +66,58 @@ package java.util; * return the head of the queue. * Exactly which element is removed from the queue is a * function of the queue's ordering policy, which differs from - * implementation to implementation. The remove() and - * poll() methods differ only in their behavior when the - * queue is empty: the remove() method throws an exception, - * while the poll() method returns null. + * implementation to implementation. The {@code remove()} and + * {@code poll()} methods differ only in their behavior when the + * queue is empty: the {@code remove()} method throws an exception, + * while the {@code poll()} method returns {@code null}. * *

The {@link #element()} and {@link #peek()} methods return, but do * not remove, the head of the queue. * - *

The Queue interface does not define the blocking queue + *

The {@code Queue} interface does not define the blocking queue * methods, which are common in concurrent programming. These methods, * which wait for elements to appear or for space to become available, are * defined in the {@link java.util.concurrent.BlockingQueue} interface, which * extends this interface. * - *

Queue implementations generally do not allow insertion - * of null elements, although some implementations, such as - * {@link LinkedList}, do not prohibit insertion of null. - * Even in the implementations that permit it, null should - * not be inserted into a Queue, as null is also - * used as a special return value by the poll method to + *

{@code Queue} implementations generally do not allow insertion + * of {@code null} elements, although some implementations, such as + * {@link LinkedList}, do not prohibit insertion of {@code null}. + * Even in the implementations that permit it, {@code null} should + * not be inserted into a {@code Queue}, as {@code null} is also + * used as a special return value by the {@code poll} method to * indicate that the queue contains no elements. * - *

Queue implementations generally do not define - * element-based versions of methods equals and - * hashCode but instead inherit the identity based versions - * from class Object, because element-based equality is not + *

{@code Queue} implementations generally do not define + * element-based versions of methods {@code equals} and + * {@code hashCode} but instead inherit the identity based versions + * from class {@code Object}, because element-based equality is not * always well-defined for queues with the same elements but different * ordering properties. * - * *

This interface is a member of the - * + * * Java Collections Framework. * - * @see java.util.Collection - * @see LinkedList - * @see PriorityQueue - * @see java.util.concurrent.LinkedBlockingQueue - * @see java.util.concurrent.BlockingQueue - * @see java.util.concurrent.ArrayBlockingQueue - * @see java.util.concurrent.LinkedBlockingQueue - * @see java.util.concurrent.PriorityBlockingQueue * @since 1.5 * @author Doug Lea - * @param the type of elements held in this collection + * @param the type of elements held in this queue */ public interface Queue extends Collection { /** * Inserts the specified element into this queue if it is possible to do so * immediately without violating capacity restrictions, returning - * true upon success and throwing an IllegalStateException + * {@code true} upon success and throwing an {@code IllegalStateException} * if no space is currently available. * * @param e the element to add - * @return true (as per the spec for {@link Collection#add}) + * @return {@code true} (as specified by {@link Collection#add}) * @throws IllegalStateException if the element cannot be added at this * time due to capacity restrictions * @throws ClassCastException if the class of the specified element * prevents it from being added to this queue * @throws NullPointerException if the specified element is null and - * this queue not permit null elements + * this queue does not permit null elements * @throws IllegalArgumentException if some property of this element * prevents it from being added to this queue */ @@ -140,8 +131,8 @@ public interface Queue extends Collec * by throwing an exception. * * @param e the element to add - * @return true if the element was added to this queue, else - * false + * @return {@code true} if the element was added to this queue, else + * {@code false} * @throws ClassCastException if the class of the specified element * prevents it from being added to this queue * @throws NullPointerException if the specified element is null and @@ -153,8 +144,8 @@ public interface Queue extends Collec /** * Retrieves and removes the head of this queue. This method differs - * from {@link #poll} only in that it throws an exception if this queue - * is empty. + * from {@link #poll poll} only in that it throws an exception if this + * queue is empty. * * @return the head of this queue * @throws NoSuchElementException if this queue is empty @@ -163,16 +154,16 @@ public interface Queue extends Collec /** * Retrieves and removes the head of this queue, - * or returns null if this queue is empty. + * or returns {@code null} if this queue is empty. * - * @return the head of this queue, or null if this queue is empty + * @return the head of this queue, or {@code null} if this queue is empty */ E poll(); /** * Retrieves, but does not remove, the head of this queue. This method - * differs from {@link #peek} only in that it throws an exception if - * this queue is empty. + * differs from {@link #peek peek} only in that it throws an exception + * if this queue is empty. * * @return the head of this queue * @throws NoSuchElementException if this queue is empty @@ -181,9 +172,9 @@ public interface Queue extends Collec /** * Retrieves, but does not remove, the head of this queue, - * or returns null if this queue is empty. + * or returns {@code null} if this queue is empty. * - * @return the head of this queue, or null if this queue is empty + * @return the head of this queue, or {@code null} if this queue is empty */ E peek(); }