Module java.base
Package java.util

Class AbstractMap.SimpleImmutableEntry<K,V>

java.lang.Object
java.util.AbstractMap.SimpleImmutableEntry<K,V>
Type Parameters:
K - the type of the keys
V - the type of the value
All Implemented Interfaces:
Serializable, Map.Entry<K,V>
Enclosing class:
AbstractMap<K,V>
public static class AbstractMap.SimpleImmutableEntry<K,V> extends Object implements Map.Entry<K,V>, Serializable
An unmodifiable Entry maintaining a key and a value. This class does not support the setValue method. Instances of this class are not associated with any map's entry-set view.
API Note:
Instances of this class are not necessarily immutable, as the key and value may be mutable. An instance of this specific class is unmodifiable, because the key and value references cannot be changed. A reference of this type may not be unmodifiable, as a subclass may be modifiable or may provide the appearance of modifiability.

This class may be convenient in methods that return thread-safe snapshots of key-value mappings. For alternatives, see the Map::entry and Map.Entry::copyOf methods.

Since:
1.6
See Also:

  • Constructor Summary

    Constructors
    Constructor
    Description
    SimpleImmutableEntry(Map.Entry<? extends K,? extends V> entry)
    Creates an entry representing the same mapping as the specified entry.
    SimpleImmutableEntry(K key, V value)
    Creates an entry representing a mapping from the specified key to the specified value.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    equals(Object o)
    Compares the specified object with this entry for equality.
    K
    getKey()
    Returns the key corresponding to this entry.
    V
    getValue()
    Returns the value corresponding to this entry.
    int
    hashCode()
    Returns the hash code value for this map entry.
    V
    setValue(V value)
    Replaces the value corresponding to this entry with the specified value (optional operation).
    String
    toString()
    Returns a String representation of this map entry.

    Methods declared in class java.lang.Object

    clone, finalize, getClass, notify, notifyAll, wait, wait, wait

  • Constructor Details

    • SimpleImmutableEntry

      public SimpleImmutableEntry(K key, V value)
      Creates an entry representing a mapping from the specified key to the specified value.
      Parameters:
      key - the key represented by this entry
      value - the value represented by this entry

    • SimpleImmutableEntry

      public SimpleImmutableEntry(Map.Entry<? extends K,? extends V> entry)
      Creates an entry representing the same mapping as the specified entry.
      Parameters:
      entry - the entry to copy

  • Method Details

    • getKey

      public K getKey()
      Returns the key corresponding to this entry.
      Specified by:
      getKey in interface Map.Entry<K,V>
      Returns:
      the key corresponding to this entry

    • getValue

      public V getValue()
      Returns the value corresponding to this entry.
      Specified by:
      getValue in interface Map.Entry<K,V>
      Returns:
      the value corresponding to this entry

    • setValue

      public V setValue(V value)
      Replaces the value corresponding to this entry with the specified value (optional operation). This implementation simply throws UnsupportedOperationException, as this class implements an unmodifiable map entry.
      Specified by:
      setValue in interface Map.Entry<K,V>
      Implementation Requirements:
      The implementation in this class always throws UnsupportedOperationException.
      Parameters:
      value - new value to be stored in this entry
      Returns:
      (Does not return)
      Throws:
      UnsupportedOperationException - always

    • equals

      public boolean equals(Object o)
      Compares the specified object with this entry for equality. Returns true if the given object is also a map entry and the two entries represent the same mapping. More formally, two entries e1 and e2 represent the same mapping if
         (e1.getKey()==null ?
    e2.getKey()==null :
    e1.getKey().equals(e2.getKey()))
   &&
   (e1.getValue()==null ?
    e2.getValue()==null :
    e1.getValue().equals(e2.getValue()))
      This ensures that the equals method works properly across different implementations of the Map.Entry interface.
      Specified by:
      equals in interface Map.Entry<K,V>
      Overrides:
      equals in class Object
      Parameters:
      o - object to be compared for equality with this map entry
      Returns:
      true if the specified object is equal to this map entry
      See Also:

    • hashCode

      public int hashCode()
      Returns the hash code value for this map entry. The hash code of a map entry e is defined to be: 
         (e.getKey()==null   ? 0 : e.getKey().hashCode()) ^
   (e.getValue()==null ? 0 : e.getValue().hashCode())
      This ensures that e1.equals(e2) implies that e1.hashCode()==e2.hashCode() for any two Entries e1 and e2, as required by the general contract of Object.hashCode().
      Specified by:
      hashCode in interface Map.Entry<K,V>
      Overrides:
      hashCode in class Object
      Returns:
      the hash code value for this map entry
      See Also:

    • toString

      public String toString()
      Returns a String representation of this map entry. This implementation returns the string representation of this entry's key followed by the equals character ("=") followed by the string representation of this entry's value.
      Overrides:
      toString in class Object
      Returns:
      a String representation of this map entry