How to Remove Element from Collection Using Iterator ?

package com.JavaInterview.Programs;

import java.util.ArrayList;

import java.util.Iterator;

import java.util.List;

import java.util.Scanner;

/**

 * Remove Element from Collection Using Iterator

 * 

 * @author:http://javainterviewprograms.blogspot.in/

 * 

 */

public class RemoveElementItrJIP {

 public static void main(String args[]) {

  List<String> JipList = new ArrayList<String>();

  JipList.add("ABC");

  JipList.add("Ram");

  JipList.add("DEF");

  JipList.add("123");

  System.out.println("The original Collection " + JipList);

  Iterator<String> itr = JipList.iterator();

  int count = 0;

  Scanner input = new Scanner(System.in);

  System.out.println("Please enter the element that you want to Remove :");

  String rmvElement = input.next();

  while (itr.hasNext()) {

   if (rmvElement.equals(itr.next())) {

    itr.remove();

    count++;

   }

  }

  if (count > 0) {

   System.out.println("After Remove:" + JipList);

  } else {

   System.out.println("No such element Exist!");

  }

  input.close();

 }

}

Output :

The original Collection [ABC, Ram, DEF, 123]

Please enter the element that you want to Remove :

123

After Remove:[ABC, Ram, DEF]

How to Search key/value in Hashtable?

package com.JavaInterview.Programs;

import java.util.Hashtable;

import java.util.Map;

import java.util.Scanner;

/**

 * Search key/value Hashtable

 * 

 * @author:http://javainterviewprograms.blogspot.in/

 * 

 */

public class HashtableKeySearch {

 public static void main(String args[]) {

  // Create Hashtable Instance

  Hashtable<Integer, String> JipHT = new Hashtable<Integer, String>();

  // Adding element to Hashtable

  JipHT.put(1, "first");

  JipHT.put(2, "second");

  JipHT.put(3, "third");

  // Print the Hashtable

  System.out.println("Original Hashtable :" + JipHT);

  Scanner input = new Scanner(System.in);

  // Search element by Key

  System.out.println("Please enter the key that you want to search :");

  int key = input.nextInt();

  if (JipHT.containsKey(key)) {

   System.out.println("The Hashtable contains the key " + key + " with value : " + JipHT.get(key));

  } else {

   System.out.println("The Hashtable dosn't contains the key");

  }

  // Search Element by Value

  Scanner input1 = new Scanner(System.in);

  Integer key1 = null;

  System.out.println("Please enter the value that you want to search :");

  String str = input1.next();

  for (Map.Entry entry : JipHT.entrySet()) {

   if (str.equals(entry.getValue())) {

    key1 = (Integer) entry.getKey();

    break;

   }

  }

  System.out.println("The key value from Hashtable for value " + str + "is :" + key1);

  input.close();

  input1.close();

 }

}

Output :

Original Hashtable :{3=third, 2=second, 1=first}

Please enter the key that you want to search :

3

The Hashtable contains the key 3 with value : third

Please enter the value that you want to search :

first

The key value from Hashtable for value firstis :1

Perform Basic Operation on Hashtable

package com.JavaInterview.Programs;

import java.util.Hashtable;

import java.util.Set;

/**

 * Perform Basic Operation on Hashtable

 * 

 * @author:http://javainterviewprograms.blogspot.in/

 * 

 */

public class HashTableBasicJIP {

 public static void main(String args[]) {

  // Create Hashtable Instance

  Hashtable<Integer, String> JipHT = new Hashtable<Integer, String>();

  // Adding element to Hashtable

  JipHT.put(1, "first");

  JipHT.put(2, "second");

  JipHT.put(3, "third");

  // Print the Hashtable

  System.out.println("Original Hashtable :"+JipHT);

  // Adding element by duplicate key

  JipHT.put(2, "six");

  System.out.println("Hashtable post duplicate key" + JipHT);

  // Adding element by duplicate value

  JipHT.put(33, "third");

  System.out.println("Hashtable post duplicate value" + JipHT);

  // getting value for given key

  System.out.println("value for the key '1'" + JipHT.get(1));

  // Check if Hashtable is empty

  System.out.println("Is Hashtable empty:" + JipHT.isEmpty());

  // Remove element from Hashtable

  JipHT.remove(1);

  System.out.println("Hashtable post removal of its elemnet " + JipHT);

  // Size of the Hashtable

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

  //Iterate through the Hashtable

  Set<Integer> keys=JipHT.keySet();

  for(Integer key:keys)

  {

   System.out.println("Value of "+key +" is "+JipHT.get(key));

  }

 }

}

Output:

Original Hashtable :{3=third, 2=second, 1=first}

Hashtable post duplicate key{3=third, 2=six, 1=first}

Hashtable post duplicate value{3=third, 2=six, 1=first, 33=third}

value for the key '1'first

Is Hashtable empty:false

Hashtable post removal of its elemnet {3=third, 2=six, 33=third}

Size of Hashtable:3

Value of 3 is third

Value of 2 is six

Value of 33 is third

How to Copy Map content to another Hashtable ?

package com.JavaInterview.Programs;

import java.util.Hashtable;

import java.util.HashMap;

/**

 * Copy Map content to another Hashtable

 * 

 * @author:http://javainterviewprograms.blogspot.in/

 * 

 */

public class CopyMapToHashTable {

 public static void main(String args[]) {

  // Create Hashtable Instance

  Hashtable<Integer, String> JipHT = new Hashtable<Integer, String>();

  // Adding element to Hashtable

  JipHT.put(1, "first");

  JipHT.put(2, "second");

  JipHT.put(3, "third");

  // Print the Hashtable

  System.out.println("Original Hashtable :" + JipHT);

  // Create HashMap

  HashMap<Integer, String> JipHM = new HashMap<Integer, String>();

  JipHM.put(5, "five");

  JipHM.put(6, "six");

  // Copying Map to Hashtable

  JipHT.putAll(JipHM);

  // Print the Hashtable

  System.out.println("Hashtable after copying :" + JipHT);

 }

}

Output:

Original Hashtable :{3=third, 2=second, 1=first}

Hashtable after copying :{6=six, 5=five, 3=third, 2=second, 1=first}

How to Iterate trough Collection Objects ?

package com.JavaInterview.Programs;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;

/**
 * Iterate trough Collection Objects
 * 
 * @author:http://javainterviewprograms.blogspot.in/
 * 
 */
public class CollectionIteratorJIP {

public static void main(String args[])
{
List<String> JipList=new ArrayList<String>();
JipList.add("ABC");
JipList.add("Ram");
JipList.add("DEF");
JipList.add("123");

Iterator<String> itr=JipList.iterator();
while(itr.hasNext())
{
System.out.println(itr.next());
}
}
}

Output:

ABC

Ram

DEF

123

Java Daemon Thread

package com.JavaInterview.Programs;

/**

 * *You can make any java thread as daemon thread. Daemon threads acts like service providers

 *  for other threads running in the same process.Daemon threads will be terminated by the 

 *  JVM when there are none of the other threads running, it includes main thread of execution 

 *  as well.

 * @author:http://javainterviewprograms.blogspot.in/

 * 

 */

public class DaemonThread extends Thread{

    

   public DaemonThread(){

       setDaemon(true);

   }

   public void run(){

       System.out.println("Is this thread Daemon? - "+isDaemon());

   }

   public static void main(String a[]){

       DaemonThread dt = new DaemonThread();

       // you can set daemon constrain here also

       // it is like dt.setDeamon(true)

       dt.start();

   }

}

Output:

Is this thread Daemon? - true

Java Thread :Extending Thread Class

package com.JavaInterview.Programs;

/* 

** A thread can be created in java by extending Thread class, where you must override run() method.

* Call start() method to start executing the thread object.

* @author:http://javainterviewprograms.blogspot.in/

* 

*/

public class ThreadExtendJIP extends Thread {

  

    public ThreadExtendJIP(String name) {

        super(name);

    }

    @Override

    public void run() {

        System.out.println("MyThread - START "+Thread.currentThread().getName());

        try {

            Thread.sleep(1000);

            //Get database connection, delete unused data from DB

            doDBProcessing();

        } catch (InterruptedException e) {

            e.printStackTrace();

        }

        System.out.println("MyThread - END "+Thread.currentThread().getName());

    }

    private void doDBProcessing() throws InterruptedException {

        Thread.sleep(5000);

    }

     

}

 class ThreadRunExample {

  

    public static void main(String[] args){

        Thread t1 = new ThreadExtendJIP("t1");

        Thread t2 = new ThreadExtendJIP("t2");

        System.out.println("Starting MyThreads");

        t1.start();

        t2.start();

        System.out.println("MyThreads has been started");

         

    }

}

Output:

Starting MyThreads

MyThreads has been started

MyThread - START t1

MyThread - START t2

MyThread - END t2

MyThread - END t1