import java.util.ArrayList;
import java.util.LinkedList;
import java.util.List;
import java.util.Iterator;
import java.util.Collection;
import java.util.Set;
import java.util.TreeSet;
import java.util.HashSet;
import java.util.Map;
import java.util.TreeMap;
import java.util.HashMap;

public class CollectionDemo
{
    public static void removeAllEvens( Collection<Integer> arr )
    {
        Iterator<Integer> itr = arr.iterator( );

        while( itr.hasNext( ) )
            if( ( itr.next( ) % 2 ) == 0 )
                itr.remove( );
    }

    public static long sum( Collection<Integer> arr )
    {
        long total = 0;

        Iterator<Integer> itr = arr.iterator( );

        while( itr.hasNext( ) )
            total += itr.next( );

        return total;
    }

    public static void main( String [ ] args )
    {
        /*
        Collection<Integer> c = new ArrayList<Integer>( );
        int N = 500000;

        long start = System.currentTimeMillis( );
        for( int i = 0; i < N; i++ )
            c.add( i );
        long sum = sum( c );
         * */
/*
        for( int i = 0; i < N; i++ )
            if( !c.contains( i ) )
                System.out.println( "OOPS!" );
*/

        /*
        long end = System.currentTimeMillis( );

        System.out.println( c );
        removeAllEvens( c );
        System.out.println( c );
        System.out.println( c.size( ) );
        System.out.println( "Sum: " + sum );
        System.out.println( "Elapsed time: " + ( end - start ) );
*/
        Map<Integer,Integer> squares = new TreeMap<Integer,Integer>( );

        for( int i = 0; i < 10; i++ )
            squares.put( i, i*i - 4*i );

        System.out.println( "KEYS: ");
        Set<Integer> keys = squares.keySet( );
        for( Integer k : keys )
            System.out.println( k );
        System.out.println( "VALUES: " );
        Collection<Integer> values = squares.values( );
        for( Integer v : values )
            System.out.println( v );

        System.out.println( "ENTRIES WRONG: ");
        for( Integer k : keys )
            System.out.println( k + "=" + squares.get( k ) );

        System.out.println( "ENTRIES RIGHT: ");
        for( Map.Entry<Integer,Integer> e : squares.entrySet( ) )
            System.out.println( e.getKey( ) + "=" + e.getValue( ) );
    }

}