org.apache.torque.om

## Class ObjectKey<T>

- java.lang.Object
- - org.apache.torque.om.ObjectKey<T>

- All Implemented Interfaces:
    Serializable, Comparable<Object>
  Direct Known Subclasses:
    ComboKey, SimpleKey

      public abstract class ObjectKey<T>
      extends Object
      implements Serializable, Comparable<Object>

  This class can be used to uniquely identify an object within an application. There are four subclasses: StringKey, NumberKey, and DateKey, and ComboKey which is a Key made up of a combination of the first three.
  Version:
    $Id: ObjectKey.java 1850965 2019-01-10 17:21:29Z painter $
  Author:
    John McNally
  See Also:
    Serialized Form

- - ### Constructor Summary

    Constructors
    Constructor and Description
    `ObjectKey()` Initializes the internal key value to `null`.

  - ### Method Summary

    All Methods Instance Methods Abstract Methods Concrete Methods
    Modifier and Type | Method and Description
    --- | ---
    `void` | `appendTo(StringBuilder sb)` Appends a String representation of the key to a buffer.
    `int` | `compareTo(Object obj)` Implements the compareTo method.
    `boolean` | `equals(Object obj)` Returns whether this ObjekctKey is equal to another Object.
    `abstract int` | `getJdbcType()` Returns the JDBC type of the key as defined in `java.sql.Types`.
    `T` | `getValue()` Get the underlying object.
    `int` | `hashCode()` Returns the hashcode of the underlying value (key), if key is not null.
    `<O extends ObjectKey<T>> void` | `setValue(O key)` Sets the internal representation to the same object used by key.
    `void` | `setValue(T key)` Sets the internal representation.
    `String` | `toString()` Get a String representation of this key.

    - ### Methods inherited from class java.lang.Object

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

- - ### Constructor Detail

    - #### ObjectKey

          public ObjectKey()

      Initializes the internal key value to `null`.

  - ### Method Detail

    - #### hashCode

          public int hashCode()

      Returns the hashcode of the underlying value (key), if key is not null. Otherwise calls Object.hashCode()
      Overrides:
        `hashCode` in class `Object`
      Returns:
        an `int` value

    - #### equals

          public boolean equals(Object obj)

      Returns whether this ObjekctKey is equal to another Object. obj is equal to this ObjectKey if obj has the same class as this ObjectKey and contains the same information this key contains. Two ObjectKeys that both contain null values are not considered equal.
      Overrides:
        `equals` in class `Object`
      Parameters:
        `obj` - the comparison value.
      Returns:
        whether the two objects are equal.

    - #### getValue

          public T getValue()

      Get the underlying object.
      Returns:
        the underlying object

    - #### getJdbcType

          public abstract int getJdbcType()

      Returns the JDBC type of the key as defined in `java.sql.Types`.
      Returns:
        the JDBC type of the key.

    - #### appendTo

          public void appendTo(StringBuilder sb)

      Appends a String representation of the key to a buffer.
      Parameters:
        `sb` - a `StringBuilder`

    - #### compareTo

          public int compareTo(Object obj)

      Implements the compareTo method.
      Specified by:
        `compareTo` in interface `Comparable<Object>`
      Parameters:
        `obj` - the object to compare to this object
      Returns:
        a numeric comparison of the two values

    - #### setValue

          public void setValue(T key)

      Sets the internal representation.
      Parameters:
        `key` - the key value

    - #### setValue

          public <O extends ObjectKey<T>> void setValue(O key)

      Sets the internal representation to the same object used by key.
      Type Parameters:
        `O` - the key type
      Parameters:
        `key` - the key value

    - #### toString

          public String toString()

      Get a String representation of this key.
      Overrides:
        `toString` in class `Object`
      Returns:
        a String representation of this key, or an empty String if the value is null.

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