//HashSetTest.java
//generate random ints, add to an hashset, display them.

//HashSet is one of the built-in classes of the Java Collections Framework.
//implements a mathematical set:
//  unique (no duplicates) objects
//  no index
//  no order
//A set is like a bag with the objects in it.  There is no notion of sequence,
// index, or order; the objects are jumbled together in the bag.
  
// Methods:
//   add(object)  won't add if a copy of the object is already in the set
//   remove(object)      
//   clear()           
//   contains(object)  
//   size()              
//   isEmpty()           
//   iterator()          itertion will be in unpredictable order

//Collections sort, reverse, shuffle can NOT be used.
//the objects in the bag are not in any order so they can't be sorted,
//reversed, or shuffled.

//HashSet is implemented with hashing which makes add, remove, and contains 
//very efficient (i.e. very fast), O(1) on average.

//User classes MUST override equals() and hashcode() to be used in a HashSet.
//see the DatesHashSetTest.java

//  http://java.sun.com/j2se/1.5.0/docs/api/java/util/HashSet.html

//***run this with 10 ints in range 5 to see the duplicates rejected and the 
//unpredictable iteration order

import java.util.*;      
import javax.swing.*;

public class HashSetTest {
    public static void main(String[] args) {
	String input;
	int size;
	int range;
	int randInt;
	
	HashSet myHashSet = new HashSet();    //***
	
	input = JOptionPane.showInputDialog( "Enter number of random ints to generate" );
	size = Integer.parseInt( input );

	input = JOptionPane.showInputDialog( "Enter upper range of the random ints" );
	range = Integer.parseInt( input );

	for (int i=1; i<=size; i++) {   
	    randInt = (int)(Math.random()*range);
	    System.out.print("generated int: " + randInt);
	    //*** add returns true if added, false if duplicate and not added
	    if (myHashSet.add(new Integer(randInt))) 
		System.out.println("   Added to set!");
	    else
		System.out.println("   Duplicate already in set. Not added to set!");
	}

	Iterator it = myHashSet.iterator();
	System.out.println("Here are your unique random integers in the set: ");
	while (it.hasNext())
	    System.out.print(it.next() + " ");    
	System.out.println();

	
        System.out.println("Min value in hash set: " + Collections.min(myHashSet));
        System.out.println("Max value in hash set: " + Collections.max(myHashSet));
    }
}