예제 #1
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  /**
   * Maps the specified <code>key</code> to the specified <code>value</code> in this hashtable.
   * Neither the key nor the value can be <code>null</code>.
   *
   * <p>The value can be retrieved by calling the <code>get</code> method with a key that is equal
   * to the original key.
   *
   * @param key the hashtable key.
   * @param value the value.
   * @return the previous value of the specified key in this hashtable, or <code>null</code> if it
   *     did not have one.
   * @exception NullPointerException if the key or value is <code>null</code>.
   * @see java.lang.Object#equals(java.lang.Object)
   * @see java.util.Hashtable#get(java.lang.Object)
   * @since JDK1.0
   */
  public Object put(Object key, Object value) {
    // Make sure the value is not null
    if (value == null) {
      throw new NullPointerException();
    }

    // Makes sure the key is not already in the hashtable.
    HashtableEntry tab[] = table;
    int hash = key.hashCode();
    int index = (hash & 0x7FFFFFFF) % tab.length;
    for (HashtableEntry e = tab[index]; e != null; e = e.next) {
      if ((e.hash == hash) && e.key.equals(key)) {
        Object old = e.value;
        e.value = value;
        return old;
      }
    }

    if (count >= threshold) {
      // Rehash the table if the threshold is exceeded
      rehash();
      return put(key, value);
    }

    // Creates the new entry.
    HashtableEntry e = new HashtableEntry();
    e.hash = hash;
    e.key = key;
    e.value = value;
    e.next = tab[index];
    tab[index] = e;
    count++;
    return null;
  }
예제 #2
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 protected Object clone() {
   HashtableEntry entry = new HashtableEntry();
   entry.hash = hash;
   entry.key = key;
   entry.value = value;
   entry.next = (next != null) ? (HashtableEntry) next.clone() : null;
   return entry;
 }
예제 #3
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 /**
  * Removes the key (and its corresponding value) from this hashtable. This method does nothing if
  * the key is not in the hashtable.
  *
  * @param key the key that needs to be removed.
  * @return the value to which the key had been mapped in this hashtable, or <code>null</code> if
  *     the key did not have a mapping.
  * @since JDK1.0
  */
 public Object remove(Object key) {
   HashtableEntry tab[] = table;
   int hash = key.hashCode();
   int index = (hash & 0x7FFFFFFF) % tab.length;
   // this loop was reviewed - code is approved!
   for (HashtableEntry e = tab[index], prev = null; e != null; prev = e, e = e.next) {
     if ((e.hash == hash) && e.key.equals(key)) {
       if (prev != null) {
         prev.next = e.next;
       } else {
         tab[index] = e.next;
       }
       count--;
       return e.value;
     }
   }
   return null;
 }
예제 #4
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  /**
   * Puts the key and the value in the table. If there already is a key equal ignore case to the one
   * passed the new value exchhanes the old one.
   *
   * @param key String key
   * @param value object to put
   * @return old value if any, or null if none
   * @exception IllegalArgumentException if key is not a string
   */
  public synchronized Object put(Object key, Object value) throws IllegalArgumentException {

    if (value == null) {
      throw new NullPointerException();
    }
    if (table == null) initTable(MIN_CAPACITY);
    try {
      // Makes sure the key is not already in the hashtable.
      int hash = hashCode((String) key);
      int index;
      HashtableEntry[] tab = null;
      do {
        tab = table;
        index = (hash & 0x7FFFFFFF) % tab.length;
        for (HashtableEntry e = tab[index]; e != null; e = e.next) {
          if ((e.hash == hash) && e.key.equalsIgnoreCase((String) key)) {
            Object old = e.value;
            e.value = value;
            return old;
          }
        }
        if (count >= threshold) {
          // Rehash the table if the threshold is exceeded
          rehash();
          continue;
        }
        break;
      } while (true);

      // Creates the new entry.
      HashtableEntry e = new HashtableEntry();
      e.hash = hash;
      e.key = (String) key;
      e.value = value;
      e.next = tab[index];
      tab[index] = e;
      count++;
      return null;
    } catch (ClassCastException cce) {
      throw new IllegalArgumentException("Non string keys are not accepted!");
    }
  }
예제 #5
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  protected void rehash() {
    int oldCapacity = table.length;
    HashtableEntry oldTable[] = table;

    int newCapacity = oldCapacity * 2 + 1;
    HashtableEntry newTable[] = new HashtableEntry[newCapacity];

    threshold = (int) (newCapacity * loadFactor);
    table = newTable;

    for (int i = oldCapacity; i-- > 0; ) {
      for (HashtableEntry old = oldTable[i]; old != null; ) {
        HashtableEntry e = old;
        old = old.next;
        int index = (e.hash & 0x7FFFFFFF) % newCapacity;
        e.next = newTable[index];
        newTable[index] = e;
      }
    }
  }
예제 #6
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  /**
   * Removes the key and its corresponding value. Key is searched case insensitively.
   *
   * @param key string key
   * @return object removed or null if none
   * @exception IllegalArgumentException if key is not s string
   */
  public synchronized Object remove(Object key) throws IllegalArgumentException {

    if (table == null) return null;
    try {
      HashtableEntry tab[] = table;
      int hash = hashCode((String) key);
      int index = (hash & 0x7FFFFFFF) % tab.length;
      for (HashtableEntry e = tab[index], prev = null; e != null; prev = e, e = e.next) {
        if ((e.hash == hash) && e.key.equalsIgnoreCase((String) key)) {
          if (prev != null) {
            prev.next = e.next;
          } else {
            tab[index] = e.next;
          }
          count--;
          return e.value;
        }
      }
      return null;
    } catch (ClassCastException cce) {
      throw new IllegalArgumentException("Non string keys are not accepted!");
    }
  }