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:
    java.util.Iterator<K>
    All Known Subinterfaces:
    OrderedMapIterator<K,​V>
    All Known Implementing Classes:
    AbstractMapIteratorDecorator, AbstractOrderedMapIteratorDecorator, EmptyMapIterator, EmptyOrderedMapIterator, EntrySetMapIterator, EntrySetToMapIteratorAdapter, UnmodifiableMapIterator, UnmodifiableOrderedMapIterator
    public interface MapIterator<K,​V>
extends java.util.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

      All Methods Instance Methods Abstract Methods 
      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 Detail

      • hasNext

        boolean hasNext()
        Checks to see if there are more entries still to be iterated.
        Specified by:
        hasNext in interface java.util.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 java.util.Iterator<K>
        Returns:
        the next key in the iteration
        Throws:
        java.util.NoSuchElementException - if the iteration is finished

      • getKey

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

      • 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 java.util.Iterator<K>
        Throws:
        java.lang.UnsupportedOperationException - if remove is not supported by the map
        java.lang.IllegalStateException - if next() has not yet been called
        java.lang.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:
        java.lang.UnsupportedOperationException - if setValue is not supported by the map
        java.lang.IllegalStateException - if next() has not yet been called
        java.lang.IllegalStateException - if remove() has been called since the last call to next()