HashMap.java

package java.util;


public class HashMap extends AbstractMap{

  //////////////////////////////////////////////////////////////
  ///// innere Klasse Null ////////////////////////////////////
  //////////////////////////////////////////////////////////////
public  class Null extends Object
    {
      public Null()
      {

      }

              public String toString()
        {
          return "Nullobject";
        }
    }


  //////////////////////////////////////////////////////////////
  ///// innere Klasse innerSet ////////////////////////////////////
  //////////////////////////////////////////////////////////////

            class ISet extends AbstractSet implements java.util.Set
        {

        Vector vec = null;

          public ISet()
          {

            vec = new Vector();

          }

          public boolean add(Object o)
          {
            vec.addElement(o);
            return true;
          }

          public int size()
          {
            return vec.size();
          }

          public Iterator iterator()
          {
            return new IIterator(vec);
          }
        }

  //////////////////////////////////////////////////////////////
  ///// innere Klasse Iterator ////////////////////////////////////
  //////////////////////////////////////////////////////////////
      class IIterator implements java.util.Iterator
        {
        int index = 0;
        Vector vec = null;
          public IIterator(Vector ve)
          {
            vec = ve;
          }

          public boolean hasNext()
          {
            if (vec.size() > index) return true;
            return false;
          }

          public Object next()
          {
            Object o = vec.elementAt(index);
            if (o==Nullobject) o=null;
            index++;
            return o;

          }

          public void remove()
          {
            index--;
            vec.removeElementAt(index);
          }

        }

  //////////////////////////////////////////////////////////////
  ///// innere Klasse Entry ////////////////////////////////////
  //////////////////////////////////////////////////////////////


      class Entry implements Map.Entry
        {
          public Object key=null;
          public Object value=null;

            public Entry(Object ke,Object valu)
            {
              key = ke;
              value = valu;
            }
            public boolean equals(Object o)
            {
              if (value == ((Entry)o).value && key == ((Entry)o).key ) return true;
              else return false;

            }

            public Object getValue()
            {
              return value;
            }

            public Object getKey()
            {
              return (Object)key;
            }

            public int hashCode()
            {
                  return value.hashCode() + key.hashCode();

            }

            public Object setValue(Object valu)
            {
              value = (String)valu;
              return this;
            }
        }

 ////////////////////////////////////////////////////////////////////

    private Hashtable m_HashTable=null;
  private Null Nullobject = null;

    public HashMap()
        {
      Nullobject = new Null();
            m_HashTable=new Hashtable();
    }

    public HashMap(int initialCapacity)
        {
      Nullobject = new Null();
            m_HashTable=new Hashtable(initialCapacity);
    }

    public HashMap(Map t)
        {
      Nullobject = new Null();
            m_HashTable=new Hashtable();
      this.putAll(t);
    }

      public void clear()
        {
            m_HashTable.clear();
        }

      public Object clone()
        {
            HashMap hm=new HashMap(this);

            return hm;
        }

    public boolean containsKey(Object key)
    {
      if (key == null) key = Nullobject;
      boolean b = m_HashTable.containsKey(key);
      return b;

    }

    public boolean containsValue(Object value)
    {
      if (value == null ) value = Nullobject;
      boolean b = m_HashTable.contains(value);
      return b;
    }

      public Set entrySet()
        {

      Object Key = null;
      ISet s = new ISet();
      Enumeration en = m_HashTable.keys();
      while (en.hasMoreElements())
        {
          Key = en.nextElement();
          s.add(new Entry(Key,m_HashTable.get(Key)));
        }
      return s;
        }

    public Object get(Object key)
    {

      if (key==null) key= Nullobject;

      Object o = m_HashTable.get(key);

      if (o == Nullobject) o=null;

      return o;
    }

    public boolean isEmpty()
    {
      return m_HashTable.isEmpty();
    }

    public Set keySet()
    {
      ISet s=new ISet();
      Enumeration en = m_HashTable.keys();

      while (en.hasMoreElements())
        {
          s.add(en.nextElement());
        }

      return s;
    }

    public Object put(Object key, Object value)
    {
      if (key==null) key=Nullobject;
      if (value==null) value = Nullobject;
      return m_HashTable.put(key,value);
    }

    public void putAll(Map m)
    {
      Iterator it = m.entrySet().iterator();
      Object key=null;
      Object value=null;

      while (it.hasNext())
        {
          Map.Entry me = (Map.Entry)it.next();
          if (me.getKey() == null) key = Nullobject;
          else key= me.getKey();
          if (me.getValue()==null) value = Nullobject;
          else value = me.getValue();
          m_HashTable.put(key,value);
        }
    }

    public Object remove(Object key)
    {
      return m_HashTable.remove(key);
    }

    public int size()
    {
      return m_HashTable.size();
    }

    public Collection values()
    {

      ISet s=new ISet();
      Enumeration en = m_HashTable.keys();

      while (en.hasMoreElements())
        {
          Object Key = en.nextElement();
          //s.add(((Map.Entry)m_HashTable.get(Key)).getValue());
          s.add(m_HashTable.get(Key));
        }
      return s;
    }
}