/**
* Associate the specified value with the specified key in this {@code Hashtable}. If the key
* already exists, the old value is replaced. The key and value cannot be null.
*
* @param key the key to add.
* @param value the value to add.
* @return the old value associated with the specified key, or {@code null} if the key did not
* exist.
* @see #elements
* @see #get
* @see #keys
* @see java.lang.Object#equals
*/
public synchronized V put(K key, V value) {
if (key == null) {
throw new NullPointerException("key == null");
} else if (value == null) {
throw new NullPointerException("value == null");
}
int hash = secondaryHash(key.hashCode());
HashtableEntry<K, V>[] tab = table;
int index = hash & (tab.length - 1);
HashtableEntry<K, V> first = tab[index];
for (HashtableEntry<K, V> e = first; e != null; e = e.next) {
if (e.hash == hash && key.equals(e.key)) {
V oldValue = e.value;
e.value = value;
return oldValue;
}
}
// No entry for key is present; create one
modCount++;
if (size++ > threshold) {
rehash(); // Does nothing!!
tab = doubleCapacity();
index = hash & (tab.length - 1);
first = tab[index];
}
tab[index] = new HashtableEntry<K, V>(key, value, hash, first);
return null;
}
/**
* Ensures that the hash table has sufficient capacity to store the specified number of mappings,
* with room to grow. If not, it increases the capacity as appropriate. Like doubleCapacity, this
* method moves existing entries to new buckets as appropriate. Unlike doubleCapacity, this method
* can grow the table by factors of 2^n for n > 1. Hopefully, a single call to this method will be
* faster than multiple calls to doubleCapacity.
*
* <p>This method is called only by putAll.
*/
private void ensureCapacity(int numMappings) {
int newCapacity = roundUpToPowerOfTwo(capacityForInitSize(numMappings));
HashtableEntry<K, V>[] oldTable = table;
int oldCapacity = oldTable.length;
if (newCapacity <= oldCapacity) {
return;
}
rehash(); // Does nothing!!
if (newCapacity == oldCapacity * 2) {
doubleCapacity();
return;
}
// We're growing by at least 4x, rehash in the obvious way
HashtableEntry<K, V>[] newTable = makeTable(newCapacity);
if (size != 0) {
int newMask = newCapacity - 1;
for (int i = 0; i < oldCapacity; i++) {
for (HashtableEntry<K, V> e = oldTable[i]; e != null; ) {
HashtableEntry<K, V> oldNext = e.next;
int newIndex = e.hash & newMask;
HashtableEntry<K, V> newNext = newTable[newIndex];
newTable[newIndex] = e;
e.next = newNext;
e = oldNext;
}
}
}
}
/**
* 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;
}
/**
* Removes the key/value pair with the specified key from this {@code Hashtable}.
*
* @param key the key to remove.
* @return the value associated with the specified key, or {@code null} if the specified key did
* not exist.
* @see #get
* @see #put
*/
public synchronized V remove(Object key) {
int hash = secondaryHash(key.hashCode());
HashtableEntry<K, V>[] tab = table;
int index = hash & (tab.length - 1);
for (HashtableEntry<K, V> e = tab[index], prev = null; e != null; prev = e, e = e.next) {
if (e.hash == hash && key.equals(e.key)) {
if (prev == null) {
tab[index] = e.next;
} else {
prev.next = e.next;
}
modCount++;
size--;
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;
}
}
}
/**
* Removes the mapping from key to value and returns true if this mapping exists; otherwise,
* returns does nothing and returns false.
*/
private synchronized boolean removeMapping(Object key, Object value) {
int hash = secondaryHash(key.hashCode());
HashtableEntry<K, V>[] tab = table;
int index = hash & (tab.length - 1);
for (HashtableEntry<K, V> e = tab[index], prev = null; e != null; prev = e, e = e.next) {
if (e.hash == hash && e.key.equals(key)) {
if (!e.value.equals(value)) {
return false; // Map has wrong value for key
}
if (prev == null) {
tab[index] = e.next;
} else {
prev.next = e.next;
}
modCount++;
size--;
return true;
}
}
return false; // No entry for key
}
/**
* This method is just like put, except that it doesn't do things that are inappropriate or
* unnecessary for constructors and pseudo-constructors (i.e., clone, readObject). In particular,
* this method does not check to ensure that capacity is sufficient, and does not increment
* modCount.
*/
private void constructorPut(K key, V value) {
if (key == null) {
throw new NullPointerException("key == null");
} else if (value == null) {
throw new NullPointerException("value == null");
}
int hash = secondaryHash(key.hashCode());
HashtableEntry<K, V>[] tab = table;
int index = hash & (tab.length - 1);
HashtableEntry<K, V> first = tab[index];
for (HashtableEntry<K, V> e = first; e != null; e = e.next) {
if (e.hash == hash && key.equals(e.key)) {
e.value = value;
return;
}
}
// No entry for key is present; create one
tab[index] = new HashtableEntry<K, V>(key, value, hash, first);
size++;
}
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!");
}
}
/**
* Doubles the capacity of the hash table. Existing entries are placed in the correct bucket on
* the enlarged table. If the current capacity is, MAXIMUM_CAPACITY, this method is a no-op.
* Returns the table, which will be new unless we were already at MAXIMUM_CAPACITY.
*/
private HashtableEntry<K, V>[] doubleCapacity() {
HashtableEntry<K, V>[] oldTable = table;
int oldCapacity = oldTable.length;
if (oldCapacity == MAXIMUM_CAPACITY) {
return oldTable;
}
int newCapacity = oldCapacity * 2;
HashtableEntry<K, V>[] newTable = makeTable(newCapacity);
if (size == 0) {
return newTable;
}
for (int j = 0; j < oldCapacity; j++) {
/*
* Rehash the bucket using the minimum number of field writes.
* This is the most subtle and delicate code in the class.
*/
HashtableEntry<K, V> e = oldTable[j];
if (e == null) {
continue;
}
int highBit = e.hash & oldCapacity;
HashtableEntry<K, V> broken = null;
newTable[j | highBit] = e;
for (HashtableEntry<K, V> n = e.next; n != null; e = n, n = n.next) {
int nextHighBit = n.hash & oldCapacity;
if (nextHighBit != highBit) {
if (broken == null) newTable[j | nextHighBit] = n;
else broken.next = n;
broken = e;
highBit = nextHighBit;
}
}
if (broken != null) broken.next = null;
}
return newTable;
}
/**
* 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!");
}
}
