hashmap in java hashmap example in java hashmap in java example concurrent hashmap in java hashmap implementation in java hashmap examples in java map and hashmap in java implementation of hashmap in java hashmap class in java difference between hashtable and hashmap in java difference between map and hashmap in java hashmap vs hashtable hashmap example in java collections hashmap in java 6 hashmap in java api hashmap in java tutorial difference between map and hashmap difference between hahstable and hashmap hashmap in java example code iterator for hashmap in java example hashmap api java 7
hashmap api java 1.6
HashMap :
1)
HashMap object organizes the data in the form of
(key, value) pairs, where keys are
distinct.
2)
HashMap follows hashing mechanism for organizing
the data in the form of (key, value)
pair.
3)
We cannot determine in which order hashmap
object displays the data i.e, undetermined
form.
4)
The operations like insertion / deletion and modification are taking more amount of
time
i.e, more expensive.
5)
Retrieval time of hashmap is more / slow.
6)
Creating the hashmap is nothing but creating the
object of Hashmap class.
Ex : HashMap hm=new HashMap();
Methods for hashmap that are inherited from Map interface. Methods in HashMap refer to
Java.Util.Map Interface
Difference between HashMap and HashTable ?
HashMap and HashTable is allows to organize the data in the form of
(key, value) pair,
belongs to 2 – D collection frame work.
HashMap
is a class implemented from Map interface, it functionality depends on
hashing
mechanism and it allows null values in (key,value) pairs, hashmap object
belongs
to non – synchronized.
HashTree is a class implemented from Dictionary interface, it
functionality depends on
hashing mechanism and it allows null values
in (key,value) pairs, hashmap object belongs to
synchronized.
The
Following program illustrate the concept of HashMap Using Iterator Interface
retrieving the data :
import java.util*;
class hm
{
Public static void main(String args[])
{
HashMap hm=new HashMap();
System.out.println(“Content of hm “+hm);
System.out.println(“size of ht “+hm.size());
//add the data to 2 –D CFW
hm.put(new Integer(10),new Float(1.5f));
hm.put(new Integer(100),new Float(2.5f));
hm.put(new Integer(1),new Float(4.5f));
hm.put(new Integer(90),new Float(11.5f));
System.out.println(“Content of hm”+hm);
System.out.println(“Size of hm”+hm.size());
// extract the data from 2 –D CFW
System.out.println(“Extract the data from hm from enrtySet()àSetà iterator”);
Set s=new hm.entrySet();
iterator itr=s.iterator();
while(itr.hasNext())
{
Object mobj=itr.next();
Map.Entry me=(Map.Entry)mobj;// Object type Casting
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;
}
System.out.println(“extract the data from htàkeySet()àSetàtoArray()”);
Set st=hm.keySet();
Object kobj1[]=st.toArray();
for(int i=0;i<kobj1.length;i++)
{
Object
vobj1=hm.get(kobj1[i]);
Integer io1=(Integer)kobj1[1]);
Float fo1=(Float)vobj1;
int acno1=io1.intValue();
float bal1=io1.floatValue();
}
}
}
Data Extraction Interfaces are as follows :
1- D and 2-D Collection Frame work classes are
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