Package org.apache.commons.collections4

Interface MapIterator<K,V>

Type Parameters:
K - the type of the keys in the map
V - the type of the values in the map
All Superinterfaces:
Iterator<K>
All Known Subinterfaces:
OrderedMapIterator<K,V>
All Known Implementing Classes:
AbstractDualBidiMap.BidiMapIterator, AbstractHashedMap.HashMapIterator, AbstractLinkedMap.LinkMapIterator, AbstractMapIteratorDecorator, AbstractOrderedMapIteratorDecorator, AbstractSortedMapDecorator.SortedMapIterator, DualTreeBidiMap.BidiOrderedMapIterator, EmptyMapIterator, EmptyOrderedMapIterator, EntrySetMapIterator, EntrySetToMapIteratorAdapter, UnmodifiableMapIterator, UnmodifiableOrderedMapIterator
public interface MapIterator<K,V> extends Iterator<K>
Defines an iterator that operates over a Map.

This iterator is a special version designed for maps. It can be more efficient to use this rather than an entry set iterator where the option is available, and it is certainly more convenient.

A map that provides this interface may not hold the data internally using Map Entry objects, thus this interface can avoid lots of object creation.

In use, this iterator iterates through the keys in the map. After each call to next(), the getValue() method provides direct access to the value. The value can also be set using setValue(). 


 MapIterator<String,Integer> it = map.mapIterator();
 while (it.hasNext()) {
   String key = it.next();
   Integer value = it.getValue();
   it.setValue(value + 1);
 }
Since:
3.0

  • Method Summary

    Modifier and Type
    Method
    Description
    K
    getKey()
    Gets the current key, which is the key returned by the last call to next().
    V
    getValue()
    Gets the current value, which is the value associated with the last key returned by next().
    boolean
    hasNext()
    Checks to see if there are more entries still to be iterated.
    K
    next()
    Gets the next key from the Map.
    void
    remove()
    Removes the last returned key from the underlying Map (optional operation).
    V
    setValue(V value)
    Sets the value associated with the current key (optional operation).

    Methods inherited from interface java.util.Iterator

    forEachRemaining

  • Method Details

    • getKey

      K getKey()
      Gets the current key, which is the key returned by the last call to next().
      Returns:
      the current key
      Throws:
      IllegalStateException - if next() has not yet been called

    • getValue

      V getValue()
      Gets the current value, which is the value associated with the last key returned by next().
      Returns:
      the current value
      Throws:
      IllegalStateException - if next() has not yet been called

    • hasNext

      boolean hasNext()
      Checks to see if there are more entries still to be iterated.
      Specified by:
      hasNext in interface Iterator<K>
      Returns:
      true if the iterator has more elements

    • next

      K next()
      Gets the next key from the Map.
      Specified by:
      next in interface Iterator<K>
      Returns:
      the next key in the iteration
      Throws:
      NoSuchElementException - if the iteration is finished

    • remove

      void remove()
      Removes the last returned key from the underlying Map (optional operation).

      This method can be called once per call to next().

      Specified by:
      remove in interface Iterator<K>
      Throws:
      UnsupportedOperationException - if remove is not supported by the map
      IllegalStateException - if next() has not yet been called
      IllegalStateException - if remove() has already been called since the last call to next()

    • setValue

      V setValue(V value)
      Sets the value associated with the current key (optional operation).
      Parameters:
      value - the new value
      Returns:
      the previous value
      Throws:
      UnsupportedOperationException - if setValue is not supported by the map
      IllegalStateException - if next() has not yet been called
      IllegalStateException - if remove() has been called since the last call to next()