1	// WISEList.java
     2	//
     3	// Exercise collections, inheritance, error handling
     4	// Ethan Bolker, for cs110 exam 2, Spring 2004
     5	
     6	import java.util.*;
     7	
     8	public abstract class WISEList
     9	{
    10	    private Set elements = new TreeSet();
    11	
    12	    public void add( Object obj ) 
    13	    {
    14		elements.add(obj);
    15	    }
    16	 
    17	    public abstract String getHeader( );
    18	   
    19	    public String getPrintableList( )
    20	    {
    21		// should do this with a StringBuffer
    22		String s = getHeader() + '\n';
    23		s += (new Date()).toString() + '\n';
    24		for (Iterator i = elements.iterator(); i.hasNext(); ) {
    25		    s += i.next().toString() + '\n';
    26		}
    27		return s;
    28	    }
    29	}