Java Elements from Hashtable Program

How to get all keys from Hashtable

package com.java2novice.hashtable;

import java.util.Hashtable;

import java.util.Set;

public class MyHashtableKeys

          {

public static void main(String a[])

{

        Hashtable hm = new Hashtable();

        hm.put("first", "First inserted");

        hm.put("second", "Second inserted");

        hm.put("third","Third inserted");

        System.out.println(hm);

        Set keys = hm.keySet();

        for(String key: keys)

       {

            System.out.println(key);

        }

    }

}

How to get entry set from Hashtable

package com.java2novice.hashtable;

import java.util.Hashtable;

import java.util.Set;

import java.util.Map.Entry;

public class MyHashtableEntrySet

{

public static void main(String a[])

{

        Hashtable hm = new Hashtable();

        hm.put("first", "First inserted");

        hm.put("second", "Second inserted");

        hm.put("third","Third inserted");

        System.out.println(hm);

        Set> entires = hm.entrySet();

        for(Entry ent:entires)

        {

            System.out.println(ent.getKey()+" ==> "+ent.getValue());

        }

    }

}

How to delete all elements from Hashtable

package com.java2novice.hashtable;

import java.util.Hashtable;

public class MyHashtableClear

{

public static void main(String a[])

{

        Hashtable hm = new Hashtable();

        hm.put("first", "First inserted");

        hm.put("second", "Second inserted");

        hm.put("third","Third inserted");

        System.out.println("My Hashtable content:");

        System.out.println(hm);

        System.out.println("Clearing Hashtable:");

        hm.clear();

        System.out.println("Content After clear:");

        System.out.println(hm);

    }

}

How to read elements using Enumeration in Hashtable

package com.java2novice.hashtable;

import java.util.Enumeration;

import java.util.Hashtable;

public class MyHashtableEnumaration

{

public static void main(String a[])

{     

        Hashtable hm = new Hashtable();

        hm.put("first", "First inserted");

        hm.put("second", "Second inserted");

        hm.put("third","Third inserted");

        Enumeration keys = hm.keys();

        while(keys.hasMoreElements())

        {

            String key = keys.nextElement();

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

        }

    }

}

Hashtable implementation with equals and hashcode

package com.java2novice.hashtable;

import java.util.Hashtable;

public class MyHashtableUserKeys

{

     public static void main(String a[])

     {

        Hashtable tm = new Hashtable();

        tm.put(new Emp(134,"Ram",3000), "Ram");

        tm.put(new Emp(235,"John",6000), "John");

        tm.put(new Emp(876,"Crish",2000), "Crish");

        tm.put(new Emp(512,"Tom",2400), "Tom");

        System.out.println("Fecthing value by creating new key:");

        Emp e = new Emp(512,"Tom",2400);

        System.out.println(e+" ==> "+tm.get(e));

    }

}

class Emp

{

    private String name;

    private int salary;

    private int id;

    public Emp(int id, String n, int s)

    {

        this.id = id;

        this.name = n;

        this.salary = s;

    }

    public String getName()

    {

        return name;

    }

    public void setName(String name)

    {

        this.name = name;

     }

    public int getSalary()

   {

        return salary;

    }

    public void setSalary(int salary)

   {

        this.salary = salary;

    }

    public String toString()

   {

        return "Id: "+this.id+" -- Name: "+this.name+" -- Salary: "+this.salary;

    }

    public void setId(int id)

    {

        this.id = id;

    }

    public int getId()

    {

        return id;

    }   

    public int hashCode()

    {

        System.out.println("In hashcode");

        return this.getId();

    }

    public boolean equals(Object obj)

    {

        Emp e = null;

        if(obj instanceof Emp)

       {

            e = (Emp) obj;

        }

        System.out.println("In equals");

        if(this.getId() == e.getId())

       {

            return true;

       }

        else

       {

            return false;

        }

    }

}