public class SparseBooleanArray extends Object implements Cloneable
Note that this container keeps its mappings in an array data structure, using a binary search to find keys. The implementation is not intended to be appropriate for data structures that may contain large numbers of items. It is generally slower than a traditional HashMap, since lookups require a binary search and adds and removes require inserting and deleting entries in the array. For containers holding up to hundreds of items, the performance difference is not significant, less than 50%.
It is possible to iterate over the items in this container using
keyAt(int)
and valueAt(int)
. Iterating over the keys using
keyAt(int)
with ascending values of the index will return the
keys in ascending order, or the values corresponding to the keys in ascending
order in the case of valueAt(int)
.
Constructor and Description |
---|
SparseBooleanArray()
Creates a new SparseBooleanArray containing no mappings.
|
SparseBooleanArray(int initialCapacity)
Creates a new SparseBooleanArray containing no mappings that will not
require any additional memory allocation to store the specified
number of mappings.
|
Modifier and Type | Method and Description |
---|---|
void |
append(int key,
boolean value)
Puts a key/value pair into the array, optimizing for the case where
the key is greater than all existing keys in the array.
|
void |
clear()
Removes all key-value mappings from this SparseBooleanArray.
|
SparseBooleanArray |
clone()
Creates and returns a copy of this object.
|
void |
delete(int key)
Removes the mapping from the specified key, if there was any.
|
boolean |
equals(Object that)
Indicates whether some other object is "equal to" this one.
|
boolean |
get(int key)
Gets the boolean mapped from the specified key, or
false
if no such mapping has been made. |
boolean |
get(int key,
boolean valueIfKeyNotFound)
Gets the boolean mapped from the specified key, or the specified value
if no such mapping has been made.
|
int |
hashCode()
Returns a hash code value for the object.
|
int |
indexOfKey(int key)
Returns the index for which
keyAt(int) would return the
specified key, or a negative number if the specified
key is not mapped. |
int |
indexOfValue(boolean value)
Returns an index for which
valueAt(int) would return the
specified key, or a negative number if no keys map to the
specified value. |
int |
keyAt(int index)
Given an index in the range
0...size()-1 , returns
the key from the index th key-value mapping that this
SparseBooleanArray stores. |
void |
put(int key,
boolean value)
Adds a mapping from the specified key to the specified value,
replacing the previous mapping from the specified key if there
was one.
|
void |
removeAt(int index) |
void |
setKeyAt(int index,
int key) |
void |
setValueAt(int index,
boolean value) |
int |
size()
Returns the number of key-value mappings that this SparseBooleanArray
currently stores.
|
String |
toString()
Returns a string representation of the object.
|
boolean |
valueAt(int index)
Given an index in the range
0...size()-1 , returns
the value from the index th key-value mapping that this
SparseBooleanArray stores. |
public SparseBooleanArray()
public SparseBooleanArray(int initialCapacity)
public SparseBooleanArray clone()
Object
x
, the expression:
will be true, and that the expression:x.clone() != x
will bex.clone().getClass() == x.getClass()
true
, but these are not absolute requirements.
While it is typically the case that:
will bex.clone().equals(x)
true
, this is not an absolute requirement.
By convention, the returned object should be obtained by calling
super.clone
. If a class and all of its superclasses (except
Object
) obey this convention, it will be the case that
x.clone().getClass() == x.getClass()
.
By convention, the object returned by this method should be independent
of this object (which is being cloned). To achieve this independence,
it may be necessary to modify one or more fields of the object returned
by super.clone
before returning it. Typically, this means
copying any mutable objects that comprise the internal "deep structure"
of the object being cloned and replacing the references to these
objects with references to the copies. If a class contains only
primitive fields or references to immutable objects, then it is usually
the case that no fields in the object returned by super.clone
need to be modified.
The method clone
for class Object
performs a
specific cloning operation. First, if the class of this object does
not implement the interface Cloneable
, then a
CloneNotSupportedException
is thrown. Note that all arrays
are considered to implement the interface Cloneable
and that
the return type of the clone
method of an array type T[]
is T[]
where T is any reference or primitive type.
Otherwise, this method creates a new instance of the class of this
object and initializes all its fields with exactly the contents of
the corresponding fields of this object, as if by assignment; the
contents of the fields are not themselves cloned. Thus, this method
performs a "shallow copy" of this object, not a "deep copy" operation.
The class Object
does not itself implement the interface
Cloneable
, so calling the clone
method on an object
whose class is Object
will result in throwing an
exception at run time.
public boolean get(int key)
false
if no such mapping has been made.public boolean get(int key, boolean valueIfKeyNotFound)
public void delete(int key)
public void removeAt(int index)
public void put(int key, boolean value)
public int size()
public int keyAt(int index)
0...size()-1
, returns
the key from the index
th key-value mapping that this
SparseBooleanArray stores.
The keys corresponding to indices in ascending order are guaranteed to
be in ascending order, e.g., keyAt(0)
will return the
smallest key and keyAt(size()-1)
will return the largest
key.
public boolean valueAt(int index)
0...size()-1
, returns
the value from the index
th key-value mapping that this
SparseBooleanArray stores.
The values corresponding to indices in ascending order are guaranteed
to be associated with keys in ascending order, e.g.,
valueAt(0)
will return the value associated with the
smallest key and valueAt(size()-1)
will return the value
associated with the largest key.
public void setValueAt(int index, boolean value)
public void setKeyAt(int index, int key)
public int indexOfKey(int key)
keyAt(int)
would return the
specified key, or a negative number if the specified
key is not mapped.public int indexOfValue(boolean value)
valueAt(int)
would return the
specified key, or a negative number if no keys map to the
specified value.
Beware that this is a linear search, unlike lookups by key,
and that multiple keys can map to the same value and this will
find only one of them.public void clear()
public void append(int key, boolean value)
public int hashCode()
Object
HashMap
.
The general contract of hashCode
is:
hashCode
method
must consistently return the same integer, provided no information
used in equals
comparisons on the object is modified.
This integer need not remain consistent from one execution of an
application to another execution of the same application.
equals(Object)
method, then calling the hashCode
method on each of
the two objects must produce the same integer result.
Object.equals(java.lang.Object)
method, then calling the hashCode
method on each of the
two objects must produce distinct integer results. However, the
programmer should be aware that producing distinct integer results
for unequal objects may improve the performance of hash tables.
As much as is reasonably practical, the hashCode method defined by
class Object
does return distinct integers for distinct
objects. (This is typically implemented by converting the internal
address of the object into an integer, but this implementation
technique is not required by the
JavaTM programming language.)
hashCode
in class Object
Object.equals(java.lang.Object)
,
System.identityHashCode(java.lang.Object)
public boolean equals(Object that)
Object
The equals
method implements an equivalence relation
on non-null object references:
x
, x.equals(x)
should return
true
.
x
and y
, x.equals(y)
should return true
if and only if
y.equals(x)
returns true
.
x
, y
, and z
, if
x.equals(y)
returns true
and
y.equals(z)
returns true
, then
x.equals(z)
should return true
.
x
and y
, multiple invocations of
x.equals(y)
consistently return true
or consistently return false
, provided no
information used in equals
comparisons on the
objects is modified.
x
,
x.equals(null)
should return false
.
The equals
method for class Object
implements
the most discriminating possible equivalence relation on objects;
that is, for any non-null reference values x
and
y
, this method returns true
if and only
if x
and y
refer to the same object
(x == y
has the value true
).
Note that it is generally necessary to override the hashCode
method whenever this method is overridden, so as to maintain the
general contract for the hashCode
method, which states
that equal objects must have equal hash codes.
equals
in class Object
that
- the reference object with which to compare.true
if this object is the same as the obj
argument; false
otherwise.Object.hashCode()
,
HashMap
public String toString()
toString
method returns a string that
"textually represents" this object. The result should
be a concise but informative representation that is easy for a
person to read.
It is recommended that all subclasses override this method.
The toString
method for class Object
returns a string consisting of the name of the class of which the
object is an instance, the at-sign character `@
', and
the unsigned hexadecimal representation of the hash code of the
object. In other words, this method returns a string equal to the
value of:
getClass().getName() + '@' + Integer.toHexString(hashCode())
This implementation composes a string by iterating over its mappings.