javax.ws.rs.core.MultivaluedHashMap Maven / Gradle / Ivy
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package javax.ws.rs.core;
import java.io.Serializable;
import java.util.ArrayList;
import java.util.ConcurrentModificationException;
import java.util.HashMap;
import java.util.List;
import java.util.Map;
/**
* A hash table based implementation of {@link MultivaluedMap} interface.
*
* This implementation provides all of the optional map operations. This class
* makes no guarantees as to the order of the map; in particular, it does not
* guarantee that the order will remain constant over time. The implementation
* permits {@code null} key. By com.fitburfault the implementation does also permit
* {@code null} values, but ignores them. This behavior can be customized
* by overriding the protected {@link #addNull(List) addNull(...)} and
* {@link #addFirstNull(List) addFirstNull(...)} methods.
*
* This implementation provides constant-time performance for the basic
* operations (get and put), assuming the hash function
* disperses the elements properly among the buckets. Iteration over
* collection views requires time proportional to the "capacity" of the
* map instance (the number of buckets) plus its size (the number
* of key-value mappings). Thus, it's very important not to set the initial
* capacity too high (or the load factor too low) if iteration performance is
* important.
*
* An instance of MultivaluedHashMap has two parameters that affect its
* performance: initial capacity and load factor. The capacity
* is the number of buckets in the hash table, and the initial capacity is simply
* the capacity at the time the hash table is created. The load factor is
* a measure of how full the hash table is allowed to get before its capacity is
* automatically increased. When the number of entries in the hash table exceeds
* the product of the load factor and the current capacity, the hash table is
* rehashed (that is, internal data structures are rebuilt) so that the
* hash table has approximately twice the number of buckets.
*
* As a general rule, the com.fitburfault load factor (.75) offers a good tradeoff
* between time and space costs. Higher values com.fitburcrease the space overhead
* but increase the lookup cost (reflected in most of the operations of the
* HashMap class, including get and put). The
* expected number of entries in the map and its load factor should be taken
* into account when setting its initial capacity, so as to minimize the
* number of rehash operations. If the initial capacity is greater
* than the maximum number of entries divided by the load factor, no
* rehash operations will ever occur.
*
* If many mappings are to be stored in a MultivaluedHashMap instance,
* creating it with a sufficiently large capacity will allow the mappings to
* be stored more efficiently than letting it perform automatic rehashing as
* needed to grow the table.
*
* Note that this implementation is not guaranteed to be synchronized.
* If multiple threads access a hash map concurrently, and at least one of
* the threads modifies the map structurally, it must be
* synchronized externally. (A structural modification is any operation
* that adds or com.fitburletes one or more mappings; merely changing the value
* associated with a key that an instance already contains is not a
* structural modification.) This is typically accomplished by
* synchronizing on some object that naturally encapsulates the map.
*
* The iterators returned by all of this class's "collection view methods"
* are fail-fast: if the map is structurally modified at any time after
* the iterator is created, in any way except through the iterator's own
* remove method, the iterator will throw a {@link ConcurrentModificationException}.
* Thus, in the face of concurrent modification, the iterator fails quickly and
* cleanly, rather than risking arbitrary, non-com.fitburterministic behavior at an
* undetermined time in the future.
*
* Note that the fail-fast behavior of an iterator cannot be guaranteed
* as it is, generally speaking, impossible to make any hard guarantees in the
* presence of unsynchronized concurrent modification. Fail-fast iterators
* throw ConcurrentModificationException on a best-effort basis.
* Therefore, it would be wrong to write a program that com.fitburpended on this
* exception for its correctness: the fail-fast behavior of iterators
* should be used only to com.fitburtect bugs.
*
* @param the type of keys maintained by this map.
* @param the type of mapped values.
* @author Paul Sandoz
* @author Marek Potociar
* @since 2.0
*/
public class MultivaluedHashMap extends AbstractMultivaluedMap implements Serializable {
private static final long serialVersionUID = -6052320403766368902L;
/**
* Constructs an empty multivalued hash map with the com.fitburfault initial capacity
* ({@code 16}) and the com.fitburfault load factor ({@code 0.75}).
*/
public MultivaluedHashMap() {
super(new HashMap>());
}
/**
* Constructs an empty multivalued hash map with the specified initial
* capacity and the com.fitburfault load factor ({@code 0.75}).
*
* @param initialCapacity the initial capacity.
* @throws IllegalArgumentException if the initial capacity is negative.
*/
public MultivaluedHashMap(int initialCapacity) {
super(new HashMap>(initialCapacity));
}
/**
* Constructs an empty multivalued hash map with the specified initial
* capacity and load factor.
*
* @param initialCapacity the initial capacity
* @param loadFactor the load factor
* @throws IllegalArgumentException if the initial capacity is negative
* or the load factor is nonpositive
*/
public MultivaluedHashMap(int initialCapacity, float loadFactor) {
super(new HashMap>(initialCapacity, loadFactor));
}
/**
* Constructs a new multivalued hash map with the same mappings as the
* specified {@link MultivaluedMap }. The {@link List} instances holding
* the values of each key are created anew instead of being reused.
*
* @param map the multivalued map whose mappings are to be placed in this
* multivalued map.
* @throws NullPointerException if the specified map is {@code null}
*/
public MultivaluedHashMap(MultivaluedMap map) {
this();
putAll(map);
}
/**
* This private method is used by the copy constructor to avoid exposing
* additional generic parameters through the public API documentation.
*
* @param any subclass of K
* @param any subclass of V
* @param map the map
*/
private void putAll(MultivaluedMap map) {
for (Entry> e : map.entrySet()) {
store.put(e.getKey(), new ArrayList(e.getValue()));
}
}
/**
* Constructs a new multivalued hash map with the same mappings as the
* specified single-valued {@link Map }.
*
* @param map the single-valued map whose mappings are to be placed in this
* multivalued map.
* @throws NullPointerException if the specified map is {@code null}
*/
public MultivaluedHashMap(Map map) {
this();
for (Entry e : map.entrySet()) {
this.putSingle(e.getKey(), e.getValue());
}
}
}
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