Java Used Pro

Simple Java Hash Set

import java.util.HashSet;

public class SimpleHashSetExample

{

public static void main(String[] args)

 {

HashSet hSet = new HashSet();

hSet.add(new Integer("1"));

hSet.add(new Integer("2"));

hSet.add(new Integer("3"));

System.out.println("HashSet contains.." + hSet);  

   }

}

Check if a particular key exists in Java Hash table

import java.util.Hashtable;

public class CheckKeyOfHashtableExample

{

public static void main(String[] args)

{

Hashtable ht = new Hashtable();

ht.put("1","One");

ht.put("2","Two");

ht.put("3","Three");

boolean blnExists = ht.containsKey("2");

System.out.println("2 exists in Hashtable ? : " + blnExists);

   }

}

Check if a particular value exists in Java Hash table

import java.util.Hashtable;

public class CheckValueOfHashtableExample

{

public static void main(String[] args)

{

Hashtable ht = new Hashtable();

ht.put("1","One");

ht.put("2","Two");

ht.put("3","Three");

boolean blnExists = ht.contains("Two");

System.out.println("Two exists in Hashtable ? : " + blnExists);

  }

}

Create Java Hash table from Hash Map

import java.util.Enumeration;

import java.util.Hashtable;

import java.util.HashMap;

public class CreateHashtableFromHashMap

{

public static void main(String[] args)

{

HashMap hMap = new HashMap();

hMap.put("1","One");

hMap.put("2","Two");

hMap.put("3","Three");

Hashtable ht = new Hashtable();

ht.put("1","This value would be Replaced !!");

ht.put("4","Four");

System.out.println("Hashtable contents before copy");

Enumeration e = ht.elements();

while(e.hasMoreElements())

System.out.println(e.nextElement());

ht.putAll(hMap);

System.out.println("Hashtable contents after copy");

e = ht.elements();

while(e.hasMoreElements())

System.out.println(e.nextElement());

     }

}

Get Collection of Values from Java Hash table

import java.util.Enumeration;

import java.util.Iterator;

import java.util.Hashtable;

import java.util.Collection;

public class GetCollectionOfValuesFromHashtableExample

{

public static void main(String[] args)

{

Hashtable ht = new Hashtable();

ht.put("1","One");

ht.put("2","Two");

ht.put("3","Three");

Collection c = ht.values();

System.out.println("Values of Collection created from Hashtable are :");

Iterator itr = c.iterator();

while(itr.hasNext())

System.out.println(itr.next());

c.remove("One");

System.out.println("Hashtable values after removal from Collection are :");

Enumeration e = ht.elements();

while(e.hasMoreElements())

System.out.println(e.nextElement());

   }

}

Get Set view of Keys from Java Hash table

import java.util.Enumeration;

import java.util.Iterator;

import java.util.Hashtable;

import java.util.Set;

   

public class GetSetViewOfKeysFromHashtableExample

{

public static void main(String[] args)

{

Hashtable ht = new Hashtable();

ht.put("1","One");

ht.put("2","Two");

ht.put("3","Three");

Set st = ht.keySet();

System.out.println("Set created from Hashtable Keys contains :");

Iterator itr = st.iterator();

while(itr.hasNext())

System.out.println(itr.next());     

st.remove("2");

System.out.println("Hashtable keys after removal from Set are :");

Enumeration e = ht.keys();

while(e.hasMoreElements())

System.out.println(e.nextElement());

   }

}

Get Size of Java Hash table

import java.util.Hashtable;

 public class GetSizeOfHashtableExample

{

 public static void main(String[] args)

{

Hashtable ht = new Hashtable();

System.out.println("Size of Hashtable : " + ht.size());

ht.put("1","One");

ht.put("2","Two");

ht.put("3","Three");

System.out.println("Size of Hashtable after addition : " + ht.size());

Object obj = ht.remove("2");

System.out.println("Size of Hashtable after removal : " + ht.size());

   }

}

Iterate through keys of Java Hash table

import java.util.Hashtable;

import java.util.Enumeration;

public class IterateThroughKeysOfHashtableExample

{

public static void main(String[] args)

{

Hashtable ht = new Hashtable();

ht.put("1","One");

ht.put("2","Two");

ht.put("3","Three");

Enumeration e = ht.keys();

while(e.hasMoreElements())

System.out.println(e.nextElement());

   }

}

Iterate through values of Java Hash table

import java.util.Hashtable;

import java.util.Enumeration;

public class IterateValuesOfHashtableExample

{

public static void main(String[] args)

{

Hashtable ht = new Hashtable();

ht.put("1","One");

ht.put("2","Two");

ht.put("3","Three");

Enumeration e = ht.elements();

while(e.hasMoreElements())

System.out.println(e.nextElement());

   }

}

Remove all values from Java Hash table

import java.util.Hashtable; 

public class EmptyHashtableExample

{

public static void main(String[] args)

{

Hashtable ht = new Hashtable();

ht.put("1","One");

ht.put("2","Two");

ht.put("3","Three");

ht.clear();

System.out.println("Total key value pairs in Hashtable are : " + ht.size());

    }

}

Remove value from Java Hash table

import java.util.Enumeration;

import java.util.Hashtable;

public class RemoveValueFromHashtableExample

{

public static void main(String[] args)

{

Hashtable ht = new Hashtable();

ht.put("1","One");

ht.put("2","Two");

ht.put("3","Three");

Object obj = ht.remove("2");

System.out.println(obj + " Removed from Hashtable");

Enumeration e = ht.elements();

while(e.hasMoreElements())

System.out.println(e.nextElement());

   }

}

Simple Java Hash table

import java.util.Hashtable;

public class SimpleHashtableExample

{

  

public static void main(String[] args)

{

Hashtable ht = new Hashtable();

ht.put("One", new Integer(1));

ht.put("Two", new Integer(2));

Object obj = ht.get("One");

System.out.println(obj);  

  }

}

Iterate through a Collection using Java Iterator

import java.util.Iterator;

import java.util.ArrayList;

public class JavaIteratorExample

 {

public static void main(String[] args)

{

ArrayList aList = new ArrayList();

aList.add("1");

aList.add("2");

aList.add("3");

aList.add("4");

aList.add("5");

Iterator itr = aList.iterator();

while(itr.hasNext())

System.out.println(itr.next());

    }

}

Iterate through elements Java Vector using Iterator

import java.util.Vector;

import java.util.Iterator;

public class IterateThroughVectorUsingIteratorExample

{

public static void main(String[] args)

{

Vector v = new Vector();

v.add("1");

v.add("2");

v.add("3");

v.add("4");

v.add("5");

Iterator itr = v.iterator();

System.out.println("Iterating through Vector elements...");

while(itr.hasNext())

System.out.println(itr.next());

   }

}