co.easimart.WeakValueHashMap Maven / Gradle / Ivy

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package co.easimart;

import java.lang.ref.WeakReference;
import java.util.HashMap;

/**
 * A HashMap where all the values are weak.
 */
/** package */ class WeakValueHashMap {
  private HashMap> map;
  
  public WeakValueHashMap() {
    map = new HashMap>();
  }

  public void put(K key, V value) {
    map.put(key, new WeakReference(value));
  }
  
  /**
   * Returns null if the key isn't in the map, or if it is an expired reference. If it is, then the
   * reference is removed from the map.
   */
  public V get(K key) {
    WeakReference reference = map.get(key);
    if (reference == null) {
      return null;
    }
    
    V value = reference.get();
    if (value == null) {
      map.remove(key);
    }
    
    return value;
  }
  
  public void remove(K key) {
    map.remove(key);
  }
  
  public void clear() {
    map.clear();
  }
}