public abstract class KeyObject
extends java.lang.Object
implements java.io.Externalizable
KeyObject
defines an characteristics of an object to be used as a key * in an ObjectIndex
. Since Java lacks true generic types, it is up to * the programmer to ensure that all KeyObject
s have the same concrete type * for a given ObjectIndex
. Each ObjectIndex
supports a single * concrete KeyObject
type. * * Concrete KeyObject
classes must always produce a
ObjectIndex
,
Serialized FormModifier and Type | Field and Description |
---|---|
static int |
KEY_EQUAL
Returned by
compareTo when the invoking key is greater than the parameter key. |
static int |
KEY_ERROR
Returned by
compareTo when the invoking key has a different type from the parameter key. |
static int |
KEY_LESS
Returned by
compareTo when the invoking key is less than the parameter key. |
static int |
KEY_MORE
Returned by
compareTo when the invoking key equals the parameter key. |
Constructor and Description |
---|
KeyObject() |
Modifier and Type | Method and Description |
---|---|
abstract int |
compareTo(KeyObject key)
Compares the invoking object to
key , returning one of the KEY_*
constants based on the relationship of the two keys. |
abstract KeyObject |
makeNullKey()
Returns a "null" (i.e., blank) key, to be used as a space-holder in certain kinds of
ObjectIndexes . |
java.lang.String |
toString()
Returns the
String representation of a KeyObject . |
public static final int KEY_LESS
compareTo
when the invoking key is less than the parameter key.
public static final int KEY_EQUAL
compareTo
when the invoking key is greater than the parameter key.
public static final int KEY_MORE
compareTo
when the invoking key equals the parameter key.
public static final int KEY_ERROR
compareTo
when the invoking key has a different type from the parameter key.
public abstract int compareTo(KeyObject key)
key
, returning one of the KEY_*
constants based on the relationship of the two keys.
key
- The key value to be compared against the invoking key. * @return One of the KEY_*
constants based on the relationship of the two keys.public abstract KeyObject makeNullKey()
ObjectIndexes
.
For example, a BTreeIndex
maintains a set of index pages that must contain
a set number of fixed-length keys. When creating a BTreeIndex
, you must provide
a "null" key, using the makeNullKey
method.
BTreeIndex
public java.lang.String toString()
String
representation of a KeyObject
.
toString
in class java.lang.Object
String
representation of a KeyObject
.