/**
* 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;
}
/**
* 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;
}
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;
}
}
}
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;
}
/**
* 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!");
}
}
/**
* 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!");
}
}