NamedOperation (Java SE 15 & JDK 15)
Description: declaration: module: jdk.dynalink, package: jdk.dynalink, class: NamedOperation
Keywords: jdk.dynalink.NamedOperation class

Module jdk.dynalink
Package jdk.dynalink

# Class NamedOperation

java.lang.Object
jdk.dynalink.NamedOperation

All Implemented Interfaces:
  `Operation`

    public final class NamedOperation
    extends Object
    implements Operation

Operation that associates a name with another operation. Typically used with operations that normally take a name or an index to bind them to a fixed name. E.g.

         new NamedOperation(
             new NamespaceOperation(
                 StandardOperation.GET,
                 StandardNamespace.PROPERTY),
             "color")

will be a named operation for getting the property named "color" on the object it is applied to, and

         new NamedOperation(
             new NamespaceOperation(
                 StandardOperation.GET,
                 StandardNamespace.ELEMENT),
             3)

will be a named operation for getting the element at index 3 from the collection it is applied to ("name" in this context is akin to "address" and encompasses both textual names, numeric indices, or any other kinds of addressing that linkers can understand). In these cases, the expected signature of the call site for the operation will change to no longer include the name parameter. Specifically, the documentation for all `StandardOperation` members describes how they are affected by being incorporated into a named operation.

While `NamedOperation` can be constructed directly, it is often convenient to use the `Operation.named(Object)` factory method instead, e.g.:

        StandardOperation.GET
            .withNamespace(StandardNamespace.ELEMENT),
            .named(3)
         )

Even though `NamedOperation` is most often used with `NamespaceOperation` as its base, it can have other operations as its base too (except another named operation). Specifically, `StandardOperation.CALL` as well as `StandardOperation.NEW` can both be used with `NamedOperation` directly. The contract for these operations is such that when they are used as named operations, their name is only used for diagnostic messages, usually containing the textual representation of the source expression that retrieved the callee, e.g. `StandardOperation.CALL.named("window.open")`.

- ## Constructor Summary

  Constructors
  Constructor | Description
  --- | ---
  `NamedOperation​(Operation baseOperation, Object name)` | Creates a new named operation.

- ## Method Summary

  Modifier and Type | Method | Description
  --- | --- | ---
  `NamedOperation` | `changeName​(String newName)` | Finds or creates a named operation that differs from this one only in the name.
  `boolean` | `equals​(Object obj)` | Compares this named operation to another object.
  `Operation` | `getBaseOperation()` | Returns the base operation of this named operation.
  `static Operation` | `getBaseOperation​(Operation op)` | If the passed operation is a named operation, returns its `getBaseOperation()`, otherwise returns the operation as is.
  `Object` | `getName()` | Returns the name of this named operation.
  `static Object` | `getName​(Operation op)` | If the passed operation is a named operation, returns its `getName()`, otherwise returns null.
  `int` | `hashCode()` | Returns the hash code of this named operation.
  `String` | `toString()` | Returns the string representation of this named operation.

  ### Methods declared in class java.lang.Object

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

  ### Methods declared in interface jdk.dynalink.Operation

  `named, withNamespace, withNamespaces`

- ## Constructor Details

  - ### NamedOperation

    public NamedOperation​(Operation baseOperation, Object name)
    Creates a new named operation.
    Parameters:
      `baseOperation` - the base operation that is associated with a name.
      `name` - the name associated with the base operation. Note that the name is not necessarily a string, but can be an arbitrary object. As the name is used for addressing, it can be an `Integer` when meant to be used as an index into an array or list etc.
    Throws:
      `NullPointerException` - if either `baseOperation` or `name` is null.
      `IllegalArgumentException` - if `baseOperation` is itself a `NamedOperation`.

- ## Method Details

  - ### getBaseOperation

    public Operation getBaseOperation()
    Returns the base operation of this named operation.
    Returns:
      the base operation of this named operation.

  - ### getName

    public Object getName()
    Returns the name of this named operation.
    Returns:
      the name of this named operation.

  - ### changeName

    public final NamedOperation changeName​(String newName)
    Finds or creates a named operation that differs from this one only in the name.
    Parameters:
      `newName` - the new name to replace the old name with.
    Returns:
      a named operation with the changed name.
    Throws:
      `NullPointerException` - if the name is null.

  - ### equals

    public boolean equals​(Object obj)
    Compares this named operation to another object. Returns true if the other object is also a named operation, and both their base operations and name are equal.
    Overrides:
      `equals` in class `Object`
    Parameters:
      `obj` - the reference object with which to compare.
    Returns:
      `true` if this object is the same as the obj argument; `false` otherwise.
    See Also:
      `Object.hashCode()`, `HashMap`

  - ### hashCode

    public int hashCode()
    Returns the hash code of this named operation. It is defined to be equal to `baseOperation.hashCode() + 31 * name.hashCode()`.
    Overrides:
      `hashCode` in class `Object`
    Returns:
      a hash code value for this object.
    See Also:
      `Object.equals(java.lang.Object)`, `System.identityHashCode(java.lang.Object)`

  - ### toString

    public String toString()
    Returns the string representation of this named operation. It is defined to be equal to `baseOperation.toString() + ":" + name.toString()`.
    Overrides:
      `toString` in class `Object`
    Returns:
      a string representation of the object.

  - ### getBaseOperation

    public static Operation getBaseOperation​(Operation op)
    If the passed operation is a named operation, returns its `getBaseOperation()`, otherwise returns the operation as is.
    Parameters:
      `op` - the operation
    Returns:
      the base operation of the passed operation.

  - ### getName

    public static Object getName​(Operation op)
    If the passed operation is a named operation, returns its `getName()`, otherwise returns null. Note that a named operation object can never have a null name, therefore returning null is indicative that the passed operation is not, in fact, a named operation.
    Parameters:
      `op` - the operation
    Returns:
      the name in the passed operation, or null if it is not a named operation.