Package org.apache.commons.lang3.tuple

Class Pair<L,​R>

  • Type Parameters:
    L - the left element type
    R - the right element type
    All Implemented Interfaces:
    java.io.Serializable, java.lang.Comparable<Pair<L,​R>>, java.util.Map.Entry<L,​R>
    Direct Known Subclasses:
    Diff, ImmutablePair, MutablePair
    public abstract class Pair<L,​R>
extends java.lang.Object
implements java.util.Map.Entry<L,​R>, java.lang.Comparable<Pair<L,​R>>, java.io.Serializable

    A pair consisting of two elements.

    This class is an abstract implementation defining the basic API. It refers to the elements as 'left' and 'right'. It also implements the Map.Entry interface where the key is 'left' and the value is 'right'.

    Subclass implementations may be mutable or immutable. However, there is no restriction on the type of the stored objects that may be stored. If mutable objects are stored in the pair, then the pair itself effectively becomes mutable.

    Since:
    3.0
    See Also:
    Serialized Form

    • Field Summary

      Fields 
      Modifier and Type Field Description
      static Pair<?,​?>[] EMPTY_ARRAY
      An empty array.

    • Constructor Summary

      Constructors 
      Constructor Description
      Pair()  

    • Method Summary

      All Methods Static Methods Instance Methods Abstract Methods Concrete Methods 
      Modifier and Type Method Description
      int compareTo​(Pair<L,​R> other)
      Compares the pair based on the left element followed by the right element.
      static <L,​R>
      Pair<L,​R>[]      		 emptyArray()
      Returns the empty array singleton that can be assigned without compiler warning.
      boolean equals​(java.lang.Object obj)
      Compares this pair to another based on the two elements.
      L getKey()
      Gets the key from this pair.
      abstract L getLeft()
      Gets the left element from this pair.
      abstract R getRight()
      Gets the right element from this pair.
      R getValue()
      Gets the value from this pair.
      int hashCode()
      Returns a suitable hash code.
      static <L,​R>
      Pair<L,​R>      		 of​(java.util.Map.Entry<L,​R> pair)
      Creates an immutable pair from an existing pair.
      static <L,​R>
      Pair<L,​R>      		 of​(L left, R right)
      Creates an immutable pair of two objects inferring the generic types.
      java.lang.String toString()
      Returns a String representation of this pair using the format ($left,$right).
      java.lang.String toString​(java.lang.String format)
      Formats the receiver using the given format.

      • Methods inherited from class java.lang.Object

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

      • Methods inherited from interface java.util.Map.Entry

        setValue

    • Field Detail

      • EMPTY_ARRAY

        public static final Pair<?,​?>[] EMPTY_ARRAY
        An empty array.

        Consider using emptyArray() to avoid generics warnings.

        Since:
        3.10.

    • Constructor Detail

      • Pair

        public Pair()

    • Method Detail

      • emptyArray

        public static <L,​R> Pair<L,​R>[] emptyArray()
        Returns the empty array singleton that can be assigned without compiler warning.
        Type Parameters:
        L - the left element type
        R - the right element type
        Returns:
        the empty array singleton that can be assigned without compiler warning.
        Since:
        3.10.

      • of

        public static <L,​R> Pair<L,​R> of​(L left,
                                             R right)

        Creates an immutable pair of two objects inferring the generic types.

        This factory allows the pair to be created using inference to obtain the generic types.

        Type Parameters:
        L - the left element type
        R - the right element type
        Parameters:
        left - the left element, may be null
        right - the right element, may be null
        Returns:
        a pair formed from the two parameters, not null

      • of

        public static <L,​R> Pair<L,​R> of​(java.util.Map.Entry<L,​R> pair)

        Creates an immutable pair from an existing pair.

        This factory allows the pair to be created using inference to obtain the generic types.

        Type Parameters:
        L - the left element type
        R - the right element type
        Parameters:
        pair - the existing pair.
        Returns:
        a pair formed from the two parameters, not null
        Since:
        3.10

      • compareTo

        public int compareTo​(Pair<L,​R> other)

        Compares the pair based on the left element followed by the right element. The types must be Comparable.

        Specified by:
        compareTo in interface java.lang.Comparable<L>
        Parameters:
        other - the other pair, not null
        Returns:
        negative if this is less, zero if equal, positive if greater

      • equals

        public boolean equals​(java.lang.Object obj)

        Compares this pair to another based on the two elements.

        Specified by:
        equals in interface java.util.Map.Entry<L,​R>
        Overrides:
        equals in class java.lang.Object
        Parameters:
        obj - the object to compare to, null returns false
        Returns:
        true if the elements of the pair are equal

      • getKey

        public final L getKey()

        Gets the key from this pair.

        This method implements the Map.Entry interface returning the left element as the key.

        Specified by:
        getKey in interface java.util.Map.Entry<L,​R>
        Returns:
        the left element as the key, may be null

      • getLeft

        public abstract L getLeft()

        Gets the left element from this pair.

        When treated as a key-value pair, this is the key.

        Returns:
        the left element, may be null

      • getRight

        public abstract R getRight()

        Gets the right element from this pair.

        When treated as a key-value pair, this is the value.

        Returns:
        the right element, may be null

      • getValue

        public R getValue()

        Gets the value from this pair.

        This method implements the Map.Entry interface returning the right element as the value.

        Specified by:
        getValue in interface java.util.Map.Entry<L,​R>
        Returns:
        the right element as the value, may be null

      • hashCode

        public int hashCode()

        Returns a suitable hash code. The hash code follows the definition in Map.Entry.

        Specified by:
        hashCode in interface java.util.Map.Entry<L,​R>
        Overrides:
        hashCode in class java.lang.Object
        Returns:
        the hash code

      • toString

        public java.lang.String toString()

        Returns a String representation of this pair using the format ($left,$right).

        Overrides:
        toString in class java.lang.Object
        Returns:
        a string describing this object, not null

      • toString

        public java.lang.String toString​(java.lang.String format)

        Formats the receiver using the given format.

        This uses Formattable to perform the formatting. Two variables may be used to embed the left and right elements. Use %1$s for the left element (key) and %2$s for the right element (value). The default format used by toString() is (%1$s,%2$s).

        Parameters:
        format - the format string, optionally containing %1$s and %2$s, not null
        Returns:
        the formatted string, not null