map interface in java map interface methods in java map interface in java collections map interface in java tutorial map interface in java example map interface in java 6 map.entry class in java map.entry in java example map.entry in java api map.entry in java 5 map.entry in java sortedmap interface java sortedmap interface example map sortedmap interface java 2 d collection frame work in java hashmap and treemap in java hashmap and treemap in java examples
2-D Collection
Frame Work :
2 – D
collection frame work is also known as double collection frame work.
Definition of 2 - D CollectionFrame Work :
A 2 – D Collection frame work is one in which
the data is organized in single
variable in the form of key, value pair.
Or
A 2 – D collection frame work is one in which the data is the form of
rows and
columns. In the key, value pair, the value of key must be unique and
the value of value is
may or may not be unique. i.e : duplicates are permitted.
In the key, value
pair the values of both key and value are by default belongs to objects of
java.lang.Object.
2 – D Collection
frame work / double / Map interfaces :
1)
Java.util.Map
2)
Java.util.Map.Entry
3)
Java.util.SortedMap
1) Java.util.Map :
Map is one of the pre defined interface present in the top most
hierarchy of 2 – D
collection frame work interface.
An object of Map interface allows us to
organize the data in the form of key, value pair.
We know in the key, value
pair the value of key represents unique and value of value
represents may or
may not be unique.
An object of Map interface always displays
data in random order. i.e: in whatever order
we add the data to Map interface
in the same order the data will be displayed.
Methods
in java.util.Map Interface :
1) Public int size() :
This method is used
for finding the number of entries present in 2 – D collection frame work
variable.
2) Public Boolean isEmpty():
This method returns
true provided no entries are present in 2 – D collection frame work
variable(Empty). This method returns false provided.
3) Public Boolean put(Object kobj,Object
vobj) :
This method is used
for adding and modifying the data to the 2 – D collection frame work variable.
While we are suing put() method, if the value of key
is not existing in 2 – D
collection frame work variable then that corresponding key, value will be
considered as inserted entry and this method returns true. While we
are using
put() method, if the value of key is already existing then the corresponding
value of value will modified with new value of value and this will be
considered as modified entry and it
returns false.
4) Public object get(Object) :
This method is used
for obtaining value of value by passing value of key.
For Example:
Object
vobj=m.get(new Integer(10));
System.out.println(vobj);
5) Public Set entrySet() :
This method is used for extracting the data from
any 2 – D collection frame work variable and it will be holding in the object
java.util.Set interface.
For Example :
System.out.println(m);//{ (10 = 1.5), (20 = 2.5), (30=1.5)}
Set
s=m.entrySet();
//s={ (10 = 1.5),
(20 = 2.5), (30=1.5)}
Iterator
itr=s.iterator();
While(itr.hasNext())
{
Object
mobj=itr.next();
Map.Entry
me=(Map.Entry)mobj;//object type casting
Object
kobj=me.getKey();
Object
vobj=me.getValue();
Integer
io=(Integer)kobj;
Float
fo=(Float)vobj;
}
6) Public Set keyset() :
This method is
used for obtaining or retrieving set of keys of any 2 – D collection frame work
variable and pass the key.
For Example :
//consider Set interface
reference s such that it contains elements as key, value pairs.
// (10,2.3), (20,2.1),
(30,3.4)
Set s=m.keySet();
Java.util.Map.Entry:
In Map.Entry, Entry is one of the predefined class and map is one of the
predefined
interface. The class Entry defined in Map interface and it can be
accessed as Map.Entry.
The
purpose of Map.Entry is to separate (key,value) pair from any 2 – D collection
frame work variable.
Methods in Entry Class :
1)
Public Object getkey()
2)
Public object getValue()
These methods are used for separating or obtaining the value’s of key and
value from
any 2 – D collection frame work variable.
3) Java.util.SortedMap :
SortedMap is one of the sub
interface of Map, so that all the methods of Map are inherited into SortedMap.
An object of SortedMap also organizes the data in the form of (key,value) pair.
An object of SortedMap always displays the data in Sorted order. sorting
process can be done based on key. In
older versions of java sorted map contain special methods except Map interface
methods. Even though methods of Map and sortedmap are same, methods of map are
defined into some predefined class in such way that the data is organized in
the form of (key,value) pair and displayed in random order.
In recent versions of java
SortedMap is containing five special methods.
1)
Public Object first()
2)
Public Object Last()
3)
Public SortedMap headMap(Object kobj)
4)
Public SortedMap subMap(Object kobj1,Object
kobj2)
5)
Pubic SortedMap tailMap(Object kobj)
2 – D Collectionframe
work classes :
2 – D Collection
frame work classes contains definition for those abstract methods which are
inherited from 2 – D collection frame work interfaces.
The following table gives 2 – D collection frame work
interface name corresponding 2 – D collection frame work class name and their
hierarchy.
From the above hierarchy we can observe that Classes which are under 2 - D collection
frame work are as following
1) HashMap
2) TreeMap
Data Extraction Interfaces are as follows :
1- D and 2-D Collection Frame work classes are
No comments:
Post a Comment