Java Using Hashset Program

Basic Hash Set Operations

package com.java2novice.hashset;

import java.util.HashSet;

public class MyBasicHashSet

{

public static void main(String a[])

{

        HashSet hs = new HashSet();

        hs.add("first");

        hs.add("second");

        hs.add("third");

        System.out.println(hs);

        System.out.println("Is HashSet empty? "+hs.isEmpty());

        hs.remove("third");

        System.out.println(hs);

        System.out.println("Size of the HashSet: "+hs.size());

        System.out.println("Does HashSet contains first element? "+hs.contains("first"));

    }

}

How to iterate through Hash Set

package com.java2novice.hashset;

import java.util.HashSet;

import java.util.Iterator;

public class MyHashSetRead

{

public static void main(String a[])

{

        HashSet hs = new HashSet();

        hs.add("first");

        hs.add("second");

        hs.add("third");

        Iterator itr = hs.iterator();

        while(itr.hasNext())

       {

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

        }

    }

}

How to copy Set content to another HashSet

package com.java2novice.hashset;

import java.util.HashSet;

public class MyHashSetCopy

{

public static void main(String a[])

{

        HashSet hs = new HashSet();

        hs.add("first");

        hs.add("second");

        hs.add("third");

        System.out.println(hs);

        HashSet subSet = new HashSet();

        subSet.add("s1");

        subSet.add("s2");

        hs.addAll(subSet);

        System.out.println("HashSet content after adding another collection:");

        System.out.println(hs);

    }

}

How to delete all elements from HashSet

package com.java2novice.hashset;

import java.util.HashSet;

public class MyHashSetClear

{

 public static void main(String a[])

{

        HashSet hs = new HashSet();

        hs.add("first");

        hs.add("second");

        hs.add("third");

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

        System.out.println(hs);

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

        hs.clear();

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

        System.out.println(hs);

    }

}

How to delete user defined objects from HashSet

package com.java2novice.hashset;

import java.util.HashSet;

public class MylhsDeleteObject

{

 public static void main(String a[])

{

        HashSet lhs = new HashSet();

        lhs.add(new Price("Banana", 20));

        lhs.add(new Price("Apple", 40));

        lhs.add(new Price("Orange", 30));

        for(Price pr:lhs)

        {

        System.out.println(pr);

        }

        Price key = new Price("Banana", 20);

        System.out.println("deleting key from set...");

        lhs.remove(key);

        System.out.println("Elements after delete:");

        for(Price pr:lhs)

        {

            System.out.println(pr);

        }

    }

}

 class Price

{

    private String item;

    private int price;

 public Price(String itm, int pr)

{

        this.item = itm;

        this.price = pr;

    }

  public int hashCode()

 {

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

        int hashcode = 0;

        hashcode = price*20;

        hashcode += item.hashCode();

        return hashcode;

    }

   public boolean equals(Object obj)

  {

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

        if (obj instanceof Price)

       {

            Price pp = (Price) obj;

            return (pp.item.equals(this.item) && pp.price == this.price);

        }

        else

       {

            return false;

        }

    }

    public String getItem()

   {

        return item;

    }

    public void setItem(String item)

   {

        this.item = item;

    }

    public int getPrice()

   {

        return price;

    }

    public void setPrice(int price)

    {

        this.price = price;

    }

     

    public String toString()

   {

        return "item: "+item+"  price: "+price;

    }

}