Can anyone please explain what this code means?

import java.util.TreeMap;
import java.util.Iterator;

//Please tell me what this class declaration means????????????
public class ST<Key extends Comparable<Key>, Val> implements Iterable<Key>
{
private TreeMap<Key, Val> st;

public ST()
{
st = new TreeMap<Key, Val>();
}

public void put(Key key, Val val)
{
if (val == null) st.remove(key);
else st.put(key, val);
}
public Val get(Key key) { return st.get(key); }
public Val remove(Key key) { return st.remove(key); }
public boolean contains(Key key) { return st.containsKey(key); }
public int size() { return st.size(); }
public Iterator<Key> iterator() { return st.keySet().iterator(); }
}