com.firefly.utils.collection.IdentityHashMap Maven / Gradle / Ivy
package com.firefly.utils.collection;
public class IdentityHashMap {
public static final int DEFAULT_TABLE_SIZE = 1024;
private final Entry[] buckets;
private final int indexMask;
public IdentityHashMap() {
this(DEFAULT_TABLE_SIZE);
}
@SuppressWarnings("unchecked")
public IdentityHashMap(int tableSize) {
this.indexMask = tableSize - 1;
this.buckets = new Entry[tableSize];
}
public final V get(K key) {
final int hash = System.identityHashCode(key);
final int bucket = hash & indexMask;
for (Entry entry = buckets[bucket]; entry != null; entry = entry.next) {
if (key == entry.key) {
return entry.value;
}
}
return null;
}
public boolean put(K key, V value) {
final int hash = System.identityHashCode(key);
final int bucket = hash & indexMask;
for (Entry entry = buckets[bucket]; entry != null; entry = entry.next) {
if (key == entry.key) {
return true;
}
}
Entry entry = new Entry<>(key, value, hash, buckets[bucket]);
buckets[bucket] = entry; // If multi-thread visits this method, perhaps the entry will be replaced by other entries.
return false;
}
public int size() {
int size = 0;
for (int i = 0; i < buckets.length; ++i) {
for (Entry entry = buckets[i]; entry != null; entry = entry.next) {
size++;
}
}
return size;
}
protected static final class Entry {
public final int hashCode;
public final K key;
public final V value;
public final Entry next;
public Entry(K key, V value, int hash, Entry next) {
this.key = key;
this.value = value;
this.next = next;
this.hashCode = hash;
}
}
}