8022087: Fix doclint issues in j.u.Deque & Queue

Reviewed-by: chegar, darcy
Contributed-by: NDoug Lea <dl@cs.oswego.edu>

src/share/classes/java/util/Deque.java

@@ -38,7 +38,7 @@ package java.util;
 /**
  * A linear collection that supports element insertion and removal at
  * both ends.  The name <i>deque</i> is short for "double ended queue"
- * and is usually pronounced "deck".  Most <tt>Deque</tt>
+ * 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.
@@ -47,10 +47,10 @@ package java.util;
  * 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 <tt>null</tt> or <tt>false</tt>, depending on
+ * 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
- * <tt>Deque</tt> implementations; in most implementations, insert
+ * {@code Deque} implementations; in most implementations, insert
  * operations cannot fail.
  *
  * <p>The twelve methods described above are summarized in the
@@ -58,6 +58,7 @@ package java.util;
  *
  * <p>
  * <table BORDER CELLPADDING=3 CELLSPACING=1>
+ * <caption>Summary of Deque methods</caption>
  *  <tr>
  *    <td></td>
  *    <td ALIGN=CENTER COLSPAN = 2> <b>First Element (Head)</b></td>
@@ -72,38 +73,39 @@ package java.util;
  *  </tr>
  *  <tr>
  *    <td><b>Insert</b></td>
- *    <td>{@link #addFirst addFirst(e)}</td>
- *    <td>{@link #offerFirst offerFirst(e)}</td>
- *    <td>{@link #addLast addLast(e)}</td>
- *    <td>{@link #offerLast offerLast(e)}</td>
+ *    <td>{@link Deque#addFirst addFirst(e)}</td>
+ *    <td>{@link Deque#offerFirst offerFirst(e)}</td>
+ *    <td>{@link Deque#addLast addLast(e)}</td>
+ *    <td>{@link Deque#offerLast offerLast(e)}</td>
  *  </tr>
  *  <tr>
  *    <td><b>Remove</b></td>
- *    <td>{@link #removeFirst removeFirst()}</td>
- *    <td>{@link #pollFirst pollFirst()}</td>
- *    <td>{@link #removeLast removeLast()}</td>
- *    <td>{@link #pollLast pollLast()}</td>
+ *    <td>{@link Deque#removeFirst removeFirst()}</td>
+ *    <td>{@link Deque#pollFirst pollFirst()}</td>
+ *    <td>{@link Deque#removeLast removeLast()}</td>
+ *    <td>{@link Deque#pollLast pollLast()}</td>
  *  </tr>
  *  <tr>
  *    <td><b>Examine</b></td>
- *    <td>{@link #getFirst getFirst()}</td>
- *    <td>{@link #peekFirst peekFirst()}</td>
- *    <td>{@link #getLast getLast()}</td>
- *    <td>{@link #peekLast peekLast()}</td>
+ *    <td>{@link Deque#getFirst getFirst()}</td>
+ *    <td>{@link Deque#peekFirst peekFirst()}</td>
+ *    <td>{@link Deque#getLast getLast()}</td>
+ *    <td>{@link Deque#peekLast peekLast()}</td>
  *  </tr>
  * </table>
  *
  * <p>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 at the end of the deque and removed from the beginning.  The methods
- * inherited from the <tt>Queue</tt> interface are precisely equivalent to
- * <tt>Deque</tt> 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:
  *
  * <p>
  * <table BORDER CELLPADDING=3 CELLSPACING=1>
+ * <caption>Comparison of Queue and Deque methods</caption>
  *  <tr>
- *    <td ALIGN=CENTER> <b><tt>Queue</tt> Method</b></td>
- *    <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
+ *    <td ALIGN=CENTER> <b>{@code Queue} Method</b></td>
+ *    <td ALIGN=CENTER> <b>Equivalent {@code Deque} Method</b></td>
  *  </tr>
  *  <tr>
  *    <td>{@link java.util.Queue#add add(e)}</td>
@@ -135,13 +137,14 @@ package java.util;
  * interface should be used in preference to the legacy {@link Stack} class.
  * When a deque is used as a stack, elements are pushed and popped from the
  * beginning of the deque.  Stack methods are precisely equivalent to
- * <tt>Deque</tt> methods as indicated in the table below:
+ * {@code Deque} methods as indicated in the table below:
  *
  * <p>
  * <table BORDER CELLPADDING=3 CELLSPACING=1>
+ * <caption>Comparison of Stack and Deque methods</caption>
  *  <tr>
  *    <td ALIGN=CENTER> <b>Stack Method</b></td>
- *    <td ALIGN=CENTER> <b>Equivalent <tt>Deque</tt> Method</b></td>
+ *    <td ALIGN=CENTER> <b>Equivalent {@code Deque} Method</b></td>
  *  </tr>
  *  <tr>
  *    <td>{@link #push push(e)}</td>
@@ -168,18 +171,18 @@ package java.util;
  * <p>Unlike the {@link List} interface, this interface does not
  * provide support for indexed access to elements.
  *
- * <p>While <tt>Deque</tt> implementations are not strictly required
+ * <p>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 <tt>Deque</tt> implementations
+ * encouraged to do so.  Users of any {@code Deque} implementations
  * that do allow null elements are strongly encouraged <i>not</i> to
  * take advantage of the ability to insert nulls.  This is so because
- * <tt>null</tt> is used as a special return value by various methods
+ * {@code null} is used as a special return value by various methods
  * to indicated that the deque is empty.
  *
- * <p><tt>Deque</tt> implementations generally do not define
- * element-based versions of the <tt>equals</tt> and <tt>hashCode</tt>
+ * <p>{@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
- * <tt>Object</tt>.
+ * {@code Object}.
  *
  * <p>This interface is a member of the <a
  * href="{@docRoot}/../technotes/guides/collections/index.html"> Java Collections
@@ -190,13 +193,13 @@ package java.util;
  * @since  1.6
  * @param <E> the type of elements held in this collection
  */
-
 public interface Deque<E> extends Queue<E> {
     /**
      * Inserts the specified element at the front of this deque if it is
-     * possible to do so immediately without violating capacity restrictions.
-     * When using a capacity-restricted deque, it is generally preferable to
-     * use method {@link #offerFirst}.
+     * possible to do so immediately without violating capacity restrictions,
+     * throwing an {@code IllegalStateException} if no space is currently
+     * available.  When using a capacity-restricted deque, it is generally
+     * preferable to use method {@link #offerFirst}.
      *
      * @param e the element to add
      * @throws IllegalStateException if the element cannot be added at this
@@ -212,9 +215,10 @@ public interface Deque<E> extends Queue<E> {
 
     /**
      * Inserts the specified element at the end of this deque if it is
-     * possible to do so immediately without violating capacity restrictions.
-     * When using a capacity-restricted deque, it is generally preferable to
-     * use method {@link #offerLast}.
+     * possible to do so immediately without violating capacity restrictions,
+     * throwing an {@code IllegalStateException} if no space is currently
+     * available.  When using a capacity-restricted deque, it is generally
+     * preferable to use method {@link #offerLast}.
      *
      * <p>This method is equivalent to {@link #add}.
      *
@@ -237,8 +241,8 @@ public interface Deque<E> extends Queue<E> {
      * which can fail to insert an element only by throwing an exception.
      *
      * @param e the element to add
-     * @return <tt>true</tt> if the element was added to this deque, else
-     *         <tt>false</tt>
+     * @return {@code true} if the element was added to this deque, else
+     *         {@code false}
      * @throws ClassCastException if the class of the specified element
      *         prevents it from being added to this deque
      * @throws NullPointerException if the specified element is null and this
@@ -255,8 +259,8 @@ public interface Deque<E> extends Queue<E> {
      * which can fail to insert an element only by throwing an exception.
      *
      * @param e the element to add
-     * @return <tt>true</tt> if the element was added to this deque, else
-     *         <tt>false</tt>
+     * @return {@code true} if the element was added to this deque, else
+     *         {@code false}
      * @throws ClassCastException if the class of the specified element
      *         prevents it from being added to this deque
      * @throws NullPointerException if the specified element is null and this
@@ -288,17 +292,17 @@ public interface Deque<E> extends Queue<E> {
 
     /**
      * Retrieves and removes the first element of this deque,
-     * or returns <tt>null</tt> if this deque is empty.
+     * or returns {@code null} if this deque is empty.
      *
-     * @return the head of this deque, or <tt>null</tt> if this deque is empty
+     * @return the head of this deque, or {@code null} if this deque is empty
      */
     E pollFirst();
 
     /**
      * Retrieves and removes the last element of this deque,
-     * or returns <tt>null</tt> if this deque is empty.
+     * or returns {@code null} if this deque is empty.
      *
-     * @return the tail of this deque, or <tt>null</tt> if this deque is empty
+     * @return the tail of this deque, or {@code null} if this deque is empty
      */
     E pollLast();
 
@@ -325,31 +329,31 @@ public interface Deque<E> extends Queue<E> {
 
     /**
      * Retrieves, but does not remove, the first element of this deque,
-     * or returns <tt>null</tt> if this deque is empty.
+     * or returns {@code null} if this deque is empty.
      *
-     * @return the head of this deque, or <tt>null</tt> if this deque is empty
+     * @return the head of this deque, or {@code null} if this deque is empty
      */
     E peekFirst();
 
     /**
      * Retrieves, but does not remove, the last element of this deque,
-     * or returns <tt>null</tt> if this deque is empty.
+     * or returns {@code null} if this deque is empty.
      *
-     * @return the tail of this deque, or <tt>null</tt> if this deque is empty
+     * @return the tail of this deque, or {@code null} if this deque is empty
      */
     E peekLast();
 
     /**
      * Removes the first occurrence of the specified element from this deque.
      * If the deque does not contain the element, it is unchanged.
-     * More formally, removes the first element <tt>e</tt> such that
+     * More formally, removes the first element {@code e} such that
      * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>
      * (if such an element exists).
-     * Returns <tt>true</tt> if this deque contained the specified element
+     * Returns {@code true} if this deque contained the specified element
      * (or equivalently, if this deque changed as a result of the call).
      *
      * @param o element to be removed from this deque, if present
-     * @return <tt>true</tt> if an element was removed as a result of this call
+     * @return {@code true} if an element was removed as a result of this call
      * @throws ClassCastException if the class of the specified element
      *         is incompatible with this deque
      * (<a href="Collection.html#optional-restrictions">optional</a>)
@@ -362,14 +366,14 @@ public interface Deque<E> extends Queue<E> {
     /**
      * Removes the last occurrence of the specified element from this deque.
      * If the deque does not contain the element, it is unchanged.
-     * More formally, removes the last element <tt>e</tt> such that
+     * More formally, removes the last element {@code e} such that
      * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>
      * (if such an element exists).
-     * Returns <tt>true</tt> if this deque contained the specified element
+     * Returns {@code true} if this deque contained the specified element
      * (or equivalently, if this deque changed as a result of the call).
      *
      * @param o element to be removed from this deque, if present
-     * @return <tt>true</tt> if an element was removed as a result of this call
+     * @return {@code true} if an element was removed as a result of this call
      * @throws ClassCastException if the class of the specified element
      *         is incompatible with this deque
      * (<a href="Collection.html#optional-restrictions">optional</a>)
@@ -385,15 +389,15 @@ public interface Deque<E> extends Queue<E> {
      * Inserts the specified element into the queue represented by this deque
      * (in other words, at the tail of this deque) if it is possible to do so
      * immediately without violating capacity restrictions, returning
-     * <tt>true</tt> upon success and throwing an
-     * <tt>IllegalStateException</tt> if no space is currently available.
+     * {@code true} upon success and throwing an
+     * {@code IllegalStateException} if no space is currently available.
      * When using a capacity-restricted deque, it is generally preferable to
      * use {@link #offer(Object) offer}.
      *
      * <p>This method is equivalent to {@link #addLast}.
      *
      * @param e the element to add
-     * @return <tt>true</tt> (as specified by {@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
@@ -409,7 +413,7 @@ public interface Deque<E> extends Queue<E> {
      * Inserts the specified element into the queue represented by this deque
      * (in other words, at the tail of this deque) if it is possible to do so
      * immediately without violating capacity restrictions, returning
-     * <tt>true</tt> upon success and <tt>false</tt> if no space is currently
+     * {@code true} upon success and {@code false} if no space is currently
      * available.  When using a capacity-restricted deque, this method is
      * generally preferable to the {@link #add} method, which can fail to
      * insert an element only by throwing an exception.
@@ -417,8 +421,8 @@ public interface Deque<E> extends Queue<E> {
      * <p>This method is equivalent to {@link #offerLast}.
      *
      * @param e the element to add
-     * @return <tt>true</tt> if the element was added to this deque, else
-     *         <tt>false</tt>
+     * @return {@code true} if the element was added to this deque, else
+     *         {@code false}
      * @throws ClassCastException if the class of the specified element
      *         prevents it from being added to this deque
      * @throws NullPointerException if the specified element is null and this
@@ -444,11 +448,11 @@ public interface Deque<E> extends Queue<E> {
     /**
      * Retrieves and removes the head of the queue represented by this deque
      * (in other words, the first element of this deque), or returns
-     * <tt>null</tt> if this deque is empty.
+     * {@code null} if this deque is empty.
      *
      * <p>This method is equivalent to {@link #pollFirst()}.
      *
-     * @return the first element of this deque, or <tt>null</tt> if
+     * @return the first element of this deque, or {@code null} if
      *         this deque is empty
      */
     E poll();
@@ -469,12 +473,12 @@ public interface Deque<E> extends Queue<E> {
     /**
      * Retrieves, but does not remove, the head of the queue represented by
      * this deque (in other words, the first element of this deque), or
-     * returns <tt>null</tt> if this deque is empty.
+     * returns {@code null} if this deque is empty.
      *
      * <p>This method is equivalent to {@link #peekFirst()}.
      *
      * @return the head of the queue represented by this deque, or
-     *         <tt>null</tt> if this deque is empty
+     *         {@code null} if this deque is empty
      */
     E peek();
 
@@ -484,9 +488,8 @@ public interface Deque<E> extends Queue<E> {
     /**
      * Pushes an element onto the stack represented by this deque (in other
      * words, at the head of this deque) if it is possible to do so
-     * immediately without violating capacity restrictions, returning
-     * <tt>true</tt> upon success and throwing an
-     * <tt>IllegalStateException</tt> if no space is currently available.
+     * immediately without violating capacity restrictions, throwing an
+     * {@code IllegalStateException} if no space is currently available.
      *
      * <p>This method is equivalent to {@link #addFirst}.
      *
@@ -520,16 +523,16 @@ public interface Deque<E> extends Queue<E> {
     /**
      * Removes the first occurrence of the specified element from this deque.
      * If the deque does not contain the element, it is unchanged.
-     * More formally, removes the first element <tt>e</tt> such that
+     * More formally, removes the first element {@code e} such that
      * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>
      * (if such an element exists).
-     * Returns <tt>true</tt> if this deque contained the specified element
+     * Returns {@code true} if this deque contained the specified element
      * (or equivalently, if this deque changed as a result of the call).
      *
-     * <p>This method is equivalent to {@link #removeFirstOccurrence}.
+     * <p>This method is equivalent to {@link #removeFirstOccurrence(Object)}.
      *
      * @param o element to be removed from this deque, if present
-     * @return <tt>true</tt> if an element was removed as a result of this call
+     * @return {@code true} if an element was removed as a result of this call
      * @throws ClassCastException if the class of the specified element
      *         is incompatible with this deque
      * (<a href="Collection.html#optional-restrictions">optional</a>)
@@ -540,13 +543,13 @@ public interface Deque<E> extends Queue<E> {
     boolean remove(Object o);
 
     /**
-     * Returns <tt>true</tt> if this deque contains the specified element.
-     * More formally, returns <tt>true</tt> if and only if this deque contains
-     * at least one element <tt>e</tt> such that
+     * Returns {@code true} if this deque contains the specified element.
+     * More formally, returns {@code true} if and only if this deque contains
+     * at least one element {@code e} such that
      * <tt>(o==null&nbsp;?&nbsp;e==null&nbsp;:&nbsp;o.equals(e))</tt>.
      *
      * @param o element whose presence in this deque is to be tested
-     * @return <tt>true</tt> if this deque contains the specified element
+     * @return {@code true} if this deque contains the specified element
      * @throws ClassCastException if the type of the specified element
      *         is incompatible with this deque
      * (<a href="Collection.html#optional-restrictions">optional</a>)

src/share/classes/java/util/Queue.java

@@ -41,14 +41,15 @@ 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 <tt>null</tt> or <tt>false</tt>, 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 <tt>Queue</tt>
+ * specifically for use with capacity-restricted {@code Queue}
  * implementations; in most implementations, insert operations cannot
  * fail.
  *
  * <p>
  * <table BORDER CELLPADDING=3 CELLSPACING=1>
+ * <caption>Summary of Queue methods</caption>
  *  <tr>
  *    <td></td>
  *    <td ALIGN=CENTER><em>Throws exception</em></td>
@@ -56,18 +57,18 @@ package java.util;
  *  </tr>
  *  <tr>
  *    <td><b>Insert</b></td>
- *    <td>{@link #add add(e)}</td>
- *    <td>{@link #offer offer(e)}</td>
+ *    <td>{@link Queue#add add(e)}</td>
+ *    <td>{@link Queue#offer offer(e)}</td>
  *  </tr>
  *  <tr>
  *    <td><b>Remove</b></td>
- *    <td>{@link #remove remove()}</td>
- *    <td>{@link #poll poll()}</td>
+ *    <td>{@link Queue#remove remove()}</td>
+ *    <td>{@link Queue#poll poll()}</td>
  *  </tr>
  *  <tr>
  *    <td><b>Examine</b></td>
- *    <td>{@link #element element()}</td>
- *    <td>{@link #peek peek()}</td>
+ *    <td>{@link Queue#element element()}</td>
+ *    <td>{@link Queue#peek peek()}</td>
  *  </tr>
  * </table>
  *
@@ -79,15 +80,15 @@ package java.util;
  * Whatever the ordering used, the <em>head</em> 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 <em> tail</em> of the queue. Other kinds of queues may use
- * different placement rules.  Every <tt>Queue</tt> implementation
+ * the <em>tail</em> of the queue. Other kinds of queues may use
+ * different placement rules.  Every {@code Queue} implementation
  * must specify its ordering properties.
  *
  * <p>The {@link #offer offer} method inserts an element if possible,
- * otherwise returning <tt>false</tt>.  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
- * <tt>offer</tt> 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 &quot;bounded&quot;) queues.
  *
@@ -95,32 +96,32 @@ 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 <tt>remove()</tt> and
- * <tt>poll()</tt> methods differ only in their behavior when the
- * queue is empty: the <tt>remove()</tt> method throws an exception,
- * while the <tt>poll()</tt> method returns <tt>null</tt>.
+ * 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}.
  *
  * <p>The {@link #element()} and {@link #peek()} methods return, but do
  * not remove, the head of the queue.
  *
- * <p>The <tt>Queue</tt> interface does not define the <i>blocking queue
+ * <p>The {@code Queue} interface does not define the <i>blocking queue
  * methods</i>, 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.
  *
- * <p><tt>Queue</tt> implementations generally do not allow insertion
- * of <tt>null</tt> elements, although some implementations, such as
- * {@link LinkedList}, do not prohibit insertion of <tt>null</tt>.
- * Even in the implementations that permit it, <tt>null</tt> should
- * not be inserted into a <tt>Queue</tt>, as <tt>null</tt> is also
- * used as a special return value by the <tt>poll</tt> method to
+ * <p>{@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.
  *
- * <p><tt>Queue</tt> implementations generally do not define
- * element-based versions of methods <tt>equals</tt> and
- * <tt>hashCode</tt> but instead inherit the identity based versions
- * from class <tt>Object</tt>, because element-based equality is not
+ * <p>{@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.
  *
@@ -145,11 +146,11 @@ public interface Queue<E> extends Collection<E> {
     /**
      * Inserts the specified element into this queue if it is possible to do so
      * immediately without violating capacity restrictions, returning
-     * <tt>true</tt> upon success and throwing an <tt>IllegalStateException</tt>
+     * {@code true} upon success and throwing an {@code IllegalStateException}
      * if no space is currently available.
      *
      * @param e the element to add
-     * @return <tt>true</tt> (as specified by {@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
@@ -169,8 +170,8 @@ public interface Queue<E> extends Collection<E> {
      * by throwing an exception.
      *
      * @param e the element to add
-     * @return <tt>true</tt> if the element was added to this queue, else
-     *         <tt>false</tt>
+     * @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
@@ -192,9 +193,9 @@ public interface Queue<E> extends Collection<E> {
 
     /**
      * Retrieves and removes the head of this queue,
-     * or returns <tt>null</tt> if this queue is empty.
+     * or returns {@code null} if this queue is empty.
      *
-     * @return the head of this queue, or <tt>null</tt> if this queue is empty
+     * @return the head of this queue, or {@code null} if this queue is empty
      */
     E poll();
 
@@ -210,9 +211,9 @@ public interface Queue<E> extends Collection<E> {
 
     /**
      * Retrieves, but does not remove, the head of this queue,
-     * or returns <tt>null</tt> if this queue is empty.
+     * or returns {@code null} if this queue is empty.
      *
-     * @return the head of this queue, or <tt>null</tt> if this queue is empty
+     * @return the head of this queue, or {@code null} if this queue is empty
      */
     E peek();
 }