--- jsr166/src/jsr166x/Deque.java 2004/12/05 21:15:31 1.3 +++ jsr166/src/jsr166x/Deque.java 2015/01/18 20:17:33 1.13 @@ -1,32 +1,34 @@ /* * Written by Doug Lea and Josh Bloch with assistance from members of * JCP JSR-166 Expert Group and released to the public domain, as explained - * at http://creativecommons.org/licenses/publicdomain + * at http://creativecommons.org/publicdomain/zero/1.0/ */ package jsr166x; // XXX This belongs in java.util!!! XXX + import java.util.*; // XXX This import goes away XXX /** - * A linear collection that supports element insertion and removal - * at both ends. The name deque is short for "double ended - * queue" and is usually pronounced "deck". Most Deque + * A linear collection that supports element insertion and removal at + * both ends. The name deque is short for "double ended queue" + * and is usually pronounced "deck". Most {@code Deque} * implementations place no fixed limits on the number of elements * they may contain, but this interface supports capacity-restricted * deques as well as those with no fixed size limit. * - *

This interface defines methods to access the elements at both ends of - * the deque. Methods are provided to insert, remove, and examine the - * element. 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 operation). The latter - * form of the insert operation is designed specifically for use with - * capacity-restricted Deque implementations; in most implementations, - * insert operations cannot fail. - * - *

The twelve methods described above are are summarized in the - * follwoing table:

- * + *

This interface defines methods to access the elements at both + * ends of the deque. Methods are provided to insert, remove, and + * examine the element. Each of these methods exists in two forms: + * one throws an exception if the operation fails, the other returns a + * special 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 + * {@code Deque} implementations; in most implementations, insert + * operations cannot fail. + * + *

The twelve methods described above are summarized in the + * following table:

+ * * * * @@ -56,9 +58,9 @@ import java.util.*; // XXX This impor * * * - * + * * - * + * * * *
Examine{@link #firstElement firstElement()}{@link #getFirst getFirst()}{@link #peekFirst peekFirst()}{@link #lastElement lastElement()}{@link #getLast getLast()}{@link #peekLast peekLast()}
@@ -66,13 +68,13 @@ import java.util.*; // XXX This impor *

This interface extends the {@link Queue} interface. When a deque is * used as a queue, FIFO (First-In-First-Out) behavior results. Elements are * added to the end of the deque and removed from the beginning. The methods - * inherited from the Queue interface are precisely equivalent to - * Deque methods as indicated in the following table:

+ * inherited from the {@code Queue} interface are precisely equivalent to + * {@code Deque} methods as indicated in the following table:

* * * - * - * + * + * * * * @@ -97,7 +99,7 @@ import java.util.*; // XXX This impor * * * - * + * * *
Queue Method Equivalent Deque Method {@code Queue} Method Equivalent {@code Deque} Method
{@link java.util.Queue#element element()}{@link #firstElement firstElement()}{@link #getFirst getFirst()}
* @@ -105,12 +107,12 @@ import java.util.*; // XXX This impor * interface should be used in preference to the legacy {@link Stack} class. * When a dequeue is used as a stack, elements are pushed and popped from the * beginning of the deque. Stack methods are precisely equivalent to - * Deque methods as indicated in the table below:

+ * {@code Deque} methods as indicated in the table below:

* * * * - * + * * * * @@ -126,28 +128,29 @@ import java.util.*; // XXX This impor * * *
Stack Method Equivalent Deque Method Equivalent {@code Deque} Method
{@link #peekFirst peekFirst()}
- *

Note that the {@link #peek peek} method works equally well when a deque - * is used as a queue or a stack; in either case, elements are drawn from the - * beginning of the deque. - * - *

This inteface provides two methods to to remove interior elements, - * {@link #removeFirstOccurrence removeFirstOccurrence} and {@link - * #removeLastOccurrence removeLastOccurrence}. Unlike the {@link List} - * interface, this interface does not provide support for indexed access to - * elements. - * - *

While Deque implementations are not strictly required to - * prohibit the insertion of null elements, they are strongly encouraged to do - * so. Users of any Deque implementations that do allow null - * elements are strongly encouraged not to take advantage of the - * ability to insert nulls. This is so because null is used as a - * special return value by various methods to indicated that the deque is - * empty. - * - *

Deque implementations generally do not define - * element-based versions of the equals and hashCode + * + *

Note that the {@link #peek peek} method works equally well when + * a deque is used as a queue or a stack; in either case, elements are + * drawn from the beginning of the deque. + * + *

This interface provides two methods to remove interior + * elements, {@link #removeFirstOccurrence removeFirstOccurrence} and + * {@link #removeLastOccurrence removeLastOccurrence}. Unlike the + * {@link List} interface, this interface does not provide support for + * indexed access to elements. + * + *

While {@code Deque} implementations are not strictly required + * to prohibit the insertion of null elements, they are strongly + * encouraged to do so. Users of any {@code Deque} implementations + * that do allow null elements are strongly encouraged not to + * take advantage of the ability to insert nulls. This is so because + * {@code null} is used as a special return value by various methods + * to indicated that the deque is empty. + * + *

{@code Deque} implementations generally do not define + * element-based versions of the {@code equals} and {@code hashCode} * methods, but instead inherit the identity-based versions from class - * Object. + * {@code Object}. * *

This interface is a member of the Java Collections @@ -162,13 +165,13 @@ public interface Deque extends Queue< /** * Inserts the specified element to the front this deque unless it would * violate capacity restrictions. When using a capacity-restricted deque, - * this method is generally preferable to method addFirst, which + * this method is generally preferable to method {@code addFirst}, which * can fail to insert an element only by throwing an exception. * * @param e the element to insert - * @return true if it was possible to insert the element, - * else false - * @throws NullPointerException if e is null and this + * @return {@code true} if it was possible to insert the element, + * else {@code false} + * @throws NullPointerException if {@code e} is null and this * deque does not permit null elements */ boolean offerFirst(E e); @@ -176,13 +179,13 @@ public interface Deque extends Queue< /** * Inserts the specified element to the end of this deque unless it would * violate capacity restrictions. When using a capacity-restricted deque, - * this method is generally preferable to method addLast which + * this method is generally preferable to method {@code addLast} which * can fail to insert an element only by throwing an exception. * * @param e the element to insert - * @return true if it was possible to insert the element, - * else false - * @throws NullPointerException if e is null and this + * @return {@code true} if it was possible to insert the element, + * else {@code false} + * @throws NullPointerException if {@code e} is null and this * deque does not permit null elements */ boolean offerLast(E e); @@ -194,7 +197,7 @@ public interface Deque extends Queue< * @param e the element to insert * @throws IllegalStateException if it was not possible to insert * the element due to capacity restrictions - * @throws NullPointerException if e is null and this + * @throws NullPointerException if {@code e} is null and this * deque does not permit null elements */ void addFirst(E e); @@ -206,32 +209,32 @@ public interface Deque extends Queue< * @param e the element to insert * @throws IllegalStateException if it was not possible to insert * the element due to capacity restrictions - * @throws NullPointerException if e is null and this + * @throws NullPointerException if {@code e} is null and this * deque does not permit null elements */ void addLast(E e); /** * Retrieves and removes the first element of this deque, or - * null if this deque is empty. + * {@code null} if this deque is empty. * - * @return the first element of this deque, or null if + * @return the first element of this deque, or {@code null} if * this deque is empty */ E pollFirst(); /** * Retrieves and removes the last element of this deque, or - * null if this deque is empty. + * {@code null} if this deque is empty. * - * @return the last element of this deque, or null if + * @return the last element of this deque, or {@code null} if * this deque is empty */ E pollLast(); /** * Removes and returns the first element of this deque. This method - * differs from the pollFirst method only in that it throws an + * differs from the {@code pollFirst} method only in that it throws an * exception if this deque is empty. * * @return the first element of this deque @@ -241,7 +244,7 @@ public interface Deque extends Queue< /** * Retrieves and removes the last element of this deque. This method - * differs from the pollLast method only in that it throws an + * differs from the {@code pollLast} method only in that it throws an * exception if this deque is empty. * * @return the last element of this deque @@ -251,65 +254,65 @@ public interface Deque extends Queue< /** * Retrieves, but does not remove, the first element of this deque, - * returning null if this deque is empty. + * returning {@code null} if this deque is empty. * - * @return the first element of this deque, or null if + * @return the first element of this deque, or {@code null} if * this deque is empty */ E peekFirst(); /** * Retrieves, but does not remove, the last element of this deque, - * returning null if this deque is empty. + * returning {@code null} if this deque is empty. * - * @return the last element of this deque, or null if this deque + * @return the last element of this deque, or {@code null} if this deque * is empty */ E peekLast(); /** * Retrieves, but does not remove, the first element of this - * deque. This method differs from the peek method only + * deque. This method differs from the {@code peek} method only * in that it throws an exception if this deque is empty. * * @return the first element of this deque * @throws NoSuchElementException if this deque is empty */ - E firstElement(); + E getFirst(); /** * Retrieves, but does not remove, the last element of this - * deque. This method differs from the peek method only + * deque. This method differs from the {@code peek} method only * in that it throws an exception if this deque is empty. * * @return the last element of this deque * @throws NoSuchElementException if this deque is empty */ - E lastElement(); + E getLast(); /** * Removes the first occurrence of the specified element in this * deque. If the deque does not contain the element, it is - * unchanged. More formally, removes the first element e - * such that (o==null ? e==null : o.equals(e)) (if + * unchanged. More formally, removes the first element {@code e} + * such that {@code (o==null ? e==null : o.equals(e))} (if * such an element exists). * * @param e element to be removed from this deque, if present - * @return true if the deque contained the specified element - * @throws NullPointerException if the specified element is null + * @return {@code true} if the deque contained the specified element + * @throws NullPointerException if the specified element is {@code null} */ boolean removeFirstOccurrence(Object e); /** * Removes the last occurrence of the specified element in this * deque. If the deque does not contain the element, it is - * unchanged. More formally, removes the last element e - * such that (o==null ? e==null : o.equals(e)) (if + * unchanged. More formally, removes the last element {@code e} + * such that {@code (o==null ? e==null : o.equals(e))} (if * such an element exists). * * @param e element to be removed from this deque, if present - * @return true if the deque contained the specified element - * @throws NullPointerException if the specified element is null + * @return {@code true} if the deque contained the specified element + * @throws NullPointerException if the specified element is {@code null} */ boolean removeLastOccurrence(Object e); @@ -327,9 +330,9 @@ public interface Deque extends Queue< *

This method is equivalent to {@link #offerLast}. * * @param e the element to insert - * @return true if it was possible to insert the element, - * else false - * @throws NullPointerException if e is null and this + * @return {@code true} if it was possible to insert the element, + * else {@code false} + * @throws NullPointerException if {@code e} is null and this * deque does not permit null elements */ boolean offer(E e); @@ -337,35 +340,35 @@ public interface Deque extends Queue< /** * Inserts the specified element into the queue represented by this * deque unless it would violate capacity restrictions. In other words, - * inserts the specified element as the last element of this deque. + * inserts the specified element as the last element of this deque. * *

This method is equivalent to {@link #addLast}. * * @param e the element to insert - * @return true (as per the spec for {@link Collection#add}) + * @return {@code true} (as per the spec for {@link Collection#add}) * @throws IllegalStateException if it was not possible to insert * the element due to capacity restrictions - * @throws NullPointerException if e is null and this + * @throws NullPointerException if {@code e} is null and this * deque does not permit null elements */ boolean add(E e); /** * Retrieves and removes the head of the queue represented by - * this deque, or null if this deque is empty. In other words, - * retrieves and removes the first element of this deque, or null + * this deque, or {@code null} if this deque is empty. In other words, + * retrieves and removes the first element of this deque, or {@code null} * if this deque is empty. * *

This method is equivalent to {@link #pollFirst()}. * - * @return the first element of this deque, or null if + * @return the first element of this deque, or {@code null} if * this deque is empty */ E poll(); /** * Retrieves and removes the head of the queue represented by this deque. - * This method differs from the poll method only in that it + * This method differs from the {@code poll} method only in that it * throws an exception if this deque is empty. * *

This method is equivalent to {@link #removeFirst()}. @@ -377,21 +380,21 @@ public interface Deque extends Queue< /** * Retrieves, but does not remove, the head of the queue represented by - * this deque, returning null if this deque is empty. + * this deque, returning {@code null} if this deque is empty. * - *

This method is equivalent to {@link #peekFirst()} + *

This method is equivalent to {@link #peekFirst()}. * * @return the head of the queue represented by this deque, or - * null if this deque is empty + * {@code null} if this deque is empty */ E peek(); /** * Retrieves, but does not remove, the head of the queue represented by - * this deque. This method differs from the peek method only in + * this deque. This method differs from the {@code peek} method only in * that it throws an exception if this deque is empty. * - *

This method is equivalent to {@link #firstElement()} + *

This method is equivalent to {@link #getFirst()}. * * @return the head of the queue represented by this deque * @throws NoSuchElementException if this deque is empty @@ -410,14 +413,14 @@ public interface Deque extends Queue< * * @throws IllegalStateException if it was not possible to insert * the element due to capacity restrictions - * @throws NullPointerException if e is null and this + * @throws NullPointerException if {@code e} is null and this * deque does not permit null elements */ void push(E e); /** * Pops an element from the stack represented by this deque. In other - * words, removes and returns the the first element of this deque. + * words, removes and returns the first element of this deque. * *

This method is equivalent to {@link #removeFirst()}. * @@ -433,8 +436,8 @@ public interface Deque extends Queue< /** * Returns an iterator over the elements in this deque. The elements * will be ordered from first (head) to last (tail). - * - * @return an Iterator over the elements in this deque + * + * @return an {@code Iterator} over the elements in this deque */ Iterator iterator(); }