Class LazyImpl<T>

java.lang.Object
org.tquadrat.foundation.lang.internal.LazyImpl<T>
Type Parameters:
T - The type of the value for this instance of Lazy.
All Implemented Interfaces:
Lazy<T>
@ClassVersion(sourceVersion="$Id: LazyImpl.java 1060 2023-09-24 19:21:40Z tquadrat $") @API(status=INTERNAL, since="0.0.5") public final class LazyImpl<T> extends Object implements Lazy<T>

The implementation of the interface Lazy.

An instance of this class holds a value that will be initialised by a call to the supplier (provided with the constructor LazyImpl(Supplier)) on a first call to get().

For special purposes, the constructor LazyImpl(Object) creates an already initialised instance of Lazy.

Use isPresent() to avoid unnecessary initialisation.

As a lazy initialisation makes the value unpredictable, it is necessary that the implementations of equals(Object) and hashCode() force the initialisation.

toString() do not force the initialisation.

Author:
Thomas Thrien (thomas.thrien@tquadrat.org)
Version:
$Id: LazyImpl.java 1060 2023-09-24 19:21:40Z tquadrat $
Since:
0.0.5
UML Diagram
UML Diagram for "org.tquadrat.foundation.lang.internal.LazyImpl"⁠

UML Diagram for "org.tquadrat.foundation.lang.internal.LazyImpl"

UML Diagram for "org.tquadrat.foundation.lang.internal.LazyImpl"⁠

  • Field Details

    • m_Lock

      private Optional<AutoLock> m_Lock
      The lock that protects the value creation. It will be set to empty after m_Value is initialised.

    • m_Supplier

      private Supplier<T> m_Supplier
      The supplier for the value of this Lazy instance. It will be set to null after m_Value is initialised.

    • m_Value

      private T m_Value
      The value of this Lazy instance; it is null if it was not yet initialised.

  • Constructor Details

    • LazyImpl

      public LazyImpl(Supplier<T> supplier)
      Creates a new Lazy instance.
      Parameters:
      supplier - The supplier that initialises the value for this instance on the first call to get().

    • LazyImpl

      public LazyImpl(T value)

      Creates a new Lazy instance that is already initialised.

      This allows to use Lazy instances also for cloneable objects, given that T is either cloneable itself or immutable.

      Parameters:
      value - The value; can be null.
      See Also:

  • Method Details

    • equals

      public final boolean equals(Object obj)
      Specified by:
      equals in interface Lazy<T>
      Overrides:
      equals in class Object

    • get

      public final T get()
      Returns the value for this instance of Lazy.
      Specified by:
      get in interface Lazy<T>
      Returns:
      The value.

    • hashCode

      public final int hashCode()
      Specified by:
      hashCode in interface Lazy<T>
      Overrides:
      hashCode in class Object

    • isPresent

      public final boolean isPresent()

      Checks whether this Lazy instance has been initialised already. But even it was initialised, Lazy.get() may still return null.

      Specified by:
      isPresent in interface Lazy<T>
      Returns:
      true if the instance was initialised, false otherwise.

    • orElseThrow

      public <X extends Throwable> T orElseThrow(Supplier<? extends X> exceptionSupplier) throws X
      Returns the value or throws the exception that is created by the given Supplier when not yet initialised.
      Specified by:
      orElseThrow in interface Lazy<T>
      Type Parameters:
      X - The type of the implementation of Throwable.
      Parameters:
      exceptionSupplier - The supplier for the exception to throw when the instance was not yet initialised.
      Returns:
      The value.
      Throws:
      X - When not initialised, the exception created by the given supplier will be thrown.

    • toString

      public final String toString()
      Specified by:
      toString in interface Lazy<T>
      Overrides:
      toString in class Object