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Oracle® Coherence Java API Reference
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## com.tangosol.util
Class NullImplementation.NullValueExtractor

    java.lang.Object
      com.tangosol.util.NullImplementation.NullValueExtractor

All Implemented Interfaces:
  ExternalizableLite, PortableObject, ValueExtractor, java.io.Serializable

Enclosing class:
  NullImplementation

    public static class NullImplementation.NullValueExtractor

extends java.lang.Object
implements ValueExtractor, java.io.Serializable, ExternalizableLite, PortableObject

A ValueExtractor that always results in the passed-in value.

Field Summary
`static NullImplementation.NullValueExtractor` | `INSTANCE` Since the ValueExtractor contains no information, only one ever has to exist.

Constructor Summary
`NullImplementation.NullValueExtractor()` Default constructor (for ExternalizableLite and PortableObject).

Method Summary
`boolean` | `equals(java.lang.Object o)` Compare the ValueExtractor with another object to determine equality.
`java.lang.Object` | `extract(java.lang.Object o)` Extract the value from the passed object.
`int` | `hashCode()` Determine a hash value for the ValueExtractor object according to the general `Object.hashCode()` contract.
`void` | `readExternal(java.io.DataInput in)` Restore the contents of this object by loading the object's state from the passed DataInput object.
`void` | `readExternal(PofReader in)` Restore the contents of a user type instance by reading its state using the specified PofReader object.
`java.lang.String` | `toString()` Provide a human-readable description of this ValueExtractor object.
`void` | `writeExternal(java.io.DataOutput out)` Save the contents of this object by storing the object's state into the passed DataOutput object.
`void` | `writeExternal(PofWriter out)` Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

Field Detail

### INSTANCE

    public static final NullImplementation.NullValueExtractor INSTANCE

  Since the ValueExtractor contains no information, only one ever has to exist.

Constructor Detail

### NullImplementation.NullValueExtractor

    public NullImplementation.NullValueExtractor()

  Default constructor (for ExternalizableLite and PortableObject).

Method Detail

### extract

    public java.lang.Object extract(java.lang.Object o)

  Extract the value from the passed object. The returned value may be null. For intrinsic types, the returned value is expected to be a standard wrapper type in the same manner that reflection works; for example, `int` would be returned as a `java.lang.Integer`.

  Specified by:
    `extract` in interface `ValueExtractor`
  Parameters:
    `o` - an Object to retrieve the value from
  Returns:
    the extracted value as an Object; null is an acceptable value
  Throws:
    `java.lang.ClassCastException` - if this ValueExtractor is incompatible with the passed object to extract a value from and the implementation requires the passed object to be of a certain type
    `WrapperException` - if this ValueExtractor encounters an exception in the course of extracting the value
    `java.lang.IllegalArgumentException` - if this ValueExtractor cannot handle the passed object for any other reason; an implementor should include a descriptive message

### equals

    public boolean equals(java.lang.Object o)

  Compare the ValueExtractor with another object to determine equality. Two ValueExtractor objects, ve1 and ve2 are considered equal iff `ve1.extract(o)` equals `ve2.extract(o)` for all values of `o`.

  Specified by:
    `equals` in interface `ValueExtractor`
  Parameters:
    `o` - the reference object with which to compare
  Returns:
    true iff this ValueExtractor and the passed object are equivalent ValueExtractors

### hashCode

    public int hashCode()

  Determine a hash value for the ValueExtractor object according to the general `Object.hashCode()` contract.

  Specified by:
    `hashCode` in interface `ValueExtractor`
  Returns:
    an integer hash value for this ValueExtractor object

### toString

    public java.lang.String toString()

  Provide a human-readable description of this ValueExtractor object.

  Specified by:
    `toString` in interface `ValueExtractor`
  Returns:
    a human-readable description of this ValueExtractor object

### readExternal

    public void readExternal(java.io.DataInput in)
                      throws java.io.IOException

  Restore the contents of this object by loading the object's state from the passed DataInput object.

  Specified by:
    `readExternal` in interface `ExternalizableLite`
  Parameters:
    `in` - the DataInput stream to read data from in order to restore the state of this object
  Throws:
    `java.io.IOException` - if an I/O exception occurs
    `java.io.NotActiveException` - if the object is not in its initial state, and therefore cannot be deserialized into

### writeExternal

    public void writeExternal(java.io.DataOutput out)
                       throws java.io.IOException

  Save the contents of this object by storing the object's state into the passed DataOutput object.

  Specified by:
    `writeExternal` in interface `ExternalizableLite`
  Parameters:
    `out` - the DataOutput stream to write the state of this object to
  Throws:
    `java.io.IOException` - if an I/O exception occurs

### readExternal

    public void readExternal(PofReader in)
                      throws java.io.IOException

  Restore the contents of a user type instance by reading its state using the specified PofReader object.

  Specified by:
    `readExternal` in interface `PortableObject`
  Parameters:
    `in` - the PofReader from which to read the object's state
  Throws:
    `java.io.IOException` - if an I/O error occurs

### writeExternal

    public void writeExternal(PofWriter out)
                       throws java.io.IOException

  Save the contents of a POF user type instance by writing its state using the specified PofWriter object.

  Specified by:
    `writeExternal` in interface `PortableObject`
  Parameters:
    `out` - the PofWriter to which to write the object's state
  Throws:
    `java.io.IOException` - if an I/O error occurs

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Oracle® Coherence Java API Reference
v3.5.3
E15583-01
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