Module org.jgrapht.core
Package org.jgrapht.util

Class CollectionUtil

java.lang.Object
org.jgrapht.util.CollectionUtil
public class CollectionUtil extends Object
Utility class to create Collection instances.
Author:
Hannes Wellmann

  • Method Details

    • newHashMapWithExpectedSize

      @Deprecated public static <K, V> HashMap<K,V> newHashMapWithExpectedSize(int expectedSize)
      Deprecated.
      Use HashMap.newHashMap(int) instead, available since Java 19.
      Returns a HashMap with an initial capacity that is sufficient to hold expectedSize mappings without rehashing its internal backing storage.

      The returned HashMap has a capacity that is the specified expected size divided by the load factor of the Map, which is sufficient to hold expectedSize mappings without rehashing. As the Javadoc of HashMap states: "If the initial capacity is greater than the maximum number of entries divided by the load factor, no rehash operations will ever occur".

      Type Parameters:
      K - the type of keys in the returned HashMap
      V - the type of values in the returned HashMap
      Parameters:
      expectedSize - of mappings that will be put into the returned HashMap
      Returns:
      an empty HashMap with sufficient capacity to hold expectedSize mappings
      See Also:

    • newLinkedHashMapWithExpectedSize

      @Deprecated public static <K, V> LinkedHashMap<K,V> newLinkedHashMapWithExpectedSize(int expectedSize)
      Deprecated.
      Use LinkedHashMap.newLinkedHashMap(int) instead, available since Java 19.
      Returns a LinkedHashMap with an initial capacity that is sufficient to hold expectedSize mappings without rehashing its internal backing storage.

      Because LinkedHashMap extends HashMap it inherits the issue that the capacity is not equivalent to the number of mappings it can hold without rehashing. See newHashMapWithExpectedSize(int) for details.

      Type Parameters:
      K - the type of keys in the returned LinkedHashMap
      V - the type of values in the returned LinkedHashMap
      Parameters:
      expectedSize - expected size of mappings that will be put into the returned LinkedHashMap
      Returns:
      an empty LinkedHashMap with sufficient capacity to hold expectedSize mappings
      See Also:

    • newHashSetWithExpectedSize

      @Deprecated public static <E> HashSet<E> newHashSetWithExpectedSize(int expectedSize)
      Deprecated.
      Use HashSet.newHashSet(int) instead, available since Java 19.
      Returns a HashSet with an initial capacity that is sufficient to hold expectedSize elements without rehashing its internal backing storage.

      Because a HashSet is backed by a HashMap it inherits the issue that the capacity is not equivalent to the number of elements it can hold without rehashing. See newHashMapWithExpectedSize(int) for details.

      Type Parameters:
      E - the type of elements in the returned HashSet
      Parameters:
      expectedSize - expected number of elements that will be add to the returned HashSet
      Returns:
      an empty HashSet with sufficient capacity to hold expectedSize elements
      See Also:

    • newLinkedHashSetWithExpectedSize

      @Deprecated public static <E> LinkedHashSet<E> newLinkedHashSetWithExpectedSize(int expectedSize)
      Deprecated.
      Use LinkedHashSet.newLinkedHashSet(int) instead, available since Java 19.
      Returns a LinkedHashSet with an initial capacity that is sufficient to hold expectedSize elements without rehashing its internal backing storage.

      Because a LinkedHashSet is backed by a HashMap it inherits the issue that the capacity is not equivalent to the number of elements it can hold without rehashing. See newHashMapWithExpectedSize(int) for details.

      Type Parameters:
      E - the type of elements in the returned LinkedHashSet
      Parameters:
      expectedSize - expected number of elements that will be add to the returned LinkedHashSet
      Returns:
      an empty LinkedHashSet with sufficient capacity to hold expectedSize elements
      See Also:

    • getElement

      public static <E> E getElement(Iterable<E> iterable, int index)
      Returns from the given Iterable the element with the given index.

      The order to which the index applies is that defined by the Iterable.iterator().

      Type Parameters:
      E - the type of elements in the Iterable
      Parameters:
      iterable - the Iterable from which the element at index is returned
      index - the index of the returned element
      Returns:
      the element with index in the iterable