236  * AbstractMap.SimpleEntry(k,v)}.
 237  *
 238  * <p>Bulk operations may complete abruptly, throwing an
 239  * exception encountered in the application of a supplied
 240  * function. Bear in mind when handling such exceptions that other
 241  * concurrently executing functions could also have thrown
 242  * exceptions, or would have done so if the first exception had
 243  * not occurred.
 244  *
 245  * <p>Speedups for parallel compared to sequential forms are common
 246  * but not guaranteed.  Parallel operations involving brief functions
 247  * on small maps may execute more slowly than sequential forms if the
 248  * underlying work to parallelize the computation is more expensive
 249  * than the computation itself.  Similarly, parallelization may not
 250  * lead to much actual parallelism if all processors are busy
 251  * performing unrelated tasks.
 252  *
 253  * <p>All arguments to all task methods must be non-null.
 254  *
 255  * <p>This class is a member of the
 256  * <a href="{@docRoot}/java/util/package-summary.html#CollectionsFramework">
 257  * Java Collections Framework</a>.
 258  *
 259  * @since 1.5
 260  * @author Doug Lea
 261  * @param <K> the type of keys maintained by this map
 262  * @param <V> the type of mapped values
 263  */
 264 public class ConcurrentHashMap<K,V> extends AbstractMap<K,V>
 265     implements ConcurrentMap<K,V>, Serializable {
 266     private static final long serialVersionUID = 7249069246763182397L;
 267 
 268     /*
 269      * Overview:
 270      *
 271      * The primary design goal of this hash table is to maintain
 272      * concurrent readability (typically method get(), but also
 273      * iterators and related methods) while minimizing update
 274      * contention. Secondary goals are to keep space consumption about
 275      * the same or better than java.util.HashMap, and to support high
 276      * initial insertion rates on an empty table by many threads.

 236  * AbstractMap.SimpleEntry(k,v)}.
 237  *
 238  * <p>Bulk operations may complete abruptly, throwing an
 239  * exception encountered in the application of a supplied
 240  * function. Bear in mind when handling such exceptions that other
 241  * concurrently executing functions could also have thrown
 242  * exceptions, or would have done so if the first exception had
 243  * not occurred.
 244  *
 245  * <p>Speedups for parallel compared to sequential forms are common
 246  * but not guaranteed.  Parallel operations involving brief functions
 247  * on small maps may execute more slowly than sequential forms if the
 248  * underlying work to parallelize the computation is more expensive
 249  * than the computation itself.  Similarly, parallelization may not
 250  * lead to much actual parallelism if all processors are busy
 251  * performing unrelated tasks.
 252  *
 253  * <p>All arguments to all task methods must be non-null.
 254  *
 255  * <p>This class is a member of the
 256  * <a href="{@docRoot}/java.base/java/util/package-summary.html#CollectionsFramework">
 257  * Java Collections Framework</a>.
 258  *
 259  * @since 1.5
 260  * @author Doug Lea
 261  * @param <K> the type of keys maintained by this map
 262  * @param <V> the type of mapped values
 263  */
 264 public class ConcurrentHashMap<K,V> extends AbstractMap<K,V>
 265     implements ConcurrentMap<K,V>, Serializable {
 266     private static final long serialVersionUID = 7249069246763182397L;
 267 
 268     /*
 269      * Overview:
 270      *
 271      * The primary design goal of this hash table is to maintain
 272      * concurrent readability (typically method get(), but also
 273      * iterators and related methods) while minimizing update
 274      * contention. Secondary goals are to keep space consumption about
 275      * the same or better than java.util.HashMap, and to support high
 276      * initial insertion rates on an empty table by many threads.