基于散列实现的HashMap
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2022-03-15 19:36:32
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public class SimpleHashMap<K, V> {
static final int SIZE = 997;
static class MapEntry<K, V> implements Map.Entry<K, V> {
private final K key;
private V value;
public MapEntry(K key, V value) {
this.key = key;
this.value = value;
}
@Override
public K getKey() {
return key;
}
@Override
public V getValue() {
return value;
}
@Override
public V setValue(V value) {
this.value = value;
return value;
}
}
@SuppressWarnings("unchecked")
LinkedList<MapEntry<K, V>>[] buckets = new LinkedList[SIZE];
private int size;
public void put(K key, V value) {
int index = hashIndexOf(key);
if(buckets[index] == null)
buckets[index] = new LinkedList<>();
LinkedList<MapEntry<K, V>> bucket = buckets[index];
if(findEntry(bucket.listIterator(), key) == null) {
bucket.add(new MapEntry<K, V>(key, value));
size ++;
}
}
private int hashIndexOf(K key) {
Objects.requireNonNull(key);
return Math.abs(key.hashCode()) % SIZE;
}
private MapEntry<K, V> findEntry(Iterator<MapEntry<K, V>> iterator, K key) {
while(iterator.hasNext()) {
MapEntry<K, V> oldMapEntry = iterator.next();
if(oldMapEntry.getKey().equals(key)) {
return oldMapEntry;
}
}
return null;
}
public V get(K key) {
ListIterator<MapEntry<K, V>> iterator = buckets[hashIndexOf(key)].listIterator();
return findEntry(iterator, key).getValue();
}
public int size() {
return size;
}
}
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