how to create a set of the values contained in Hashtable using collections in java
how to create a set of the values contained in Hashtable using collections in java
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In this example we will see how to create a Set of the elements that are contained in a Hashtable.
For creating a Hashtable first of all we have to import the java.util package in which the java.util.Hashtable class is defined. In this example we have created a class named CollectionExample in which we have created a Hashtable and added some elements to it.
In this example we have used the entrySet() method on the object of the Hashtable for creating a set of the values of the Hashtable. The general syntax of the entrySet() method is as follows,
Set entrySet()
This method returns a Set view of the entries contained in the created Hashtable.
In this example we have created a Hashtable and added some elements to it. Then we created a Set of the values contained in the Hashtable using the entrySet() method on the object of the Hashtable.
package r4r.co.in;
import java.util.*;
public class CollectionExample {
/**
* @param args
*/
public static void main(String[] args) throws NullPointerException
{
// TODO Auto-generated method stub
try
{
Hashtable<Integer,String> ht=new Hashtable<Integer,String>(); // created a Hashtable named ht in which key is numeric and value is String types
ht.put(1, "r4r"); // adding the values to the hashtable using key-value pairs
ht.put(2, "development");
ht.put(3, "tutorials");
ht.put(4, "shashi");
ht.put(5, "software developer");
System.out.println("The size of the Hashtable ht is: "+ht.size()); // displaying the size of the Hashtable
System.out.println("The elements according to key are: ");
for(int i=1;i<=ht.size();i++)
{
System.out.println("key = "+i+","+"Value = "+ ht.get(i)); // displaying the key-value pair contained in the Hashtable
}
System.out.println("The set of values containing contents of Hashtable is: "+ht.entrySet()); // creating a set for containing the contents of a Hashtable using entrySet() method
}
catch(NullPointerException e) // handling the NullPointer Exception which is thrown
{
e.printStackTrace();
}
}
}
The output of the above created example is given below:
The size of the Hashtable ht is: 5
The elements according to key are:
key = 1,Value = r4r
key = 2,Value = development
key = 3,Value = tutorials
key = 4,Value = shashi
key = 5,Value = software developer
The set of values containing contents of Hashtable is: [5=software developer, 4=shashi, 3=tutorials, 2=development, 1=r4r]
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