HashMap to return default value for non-found keys?

In Java 8, use Map.getOrDefault. It takes the key, and the value to return if no matching key is found.

[Update]

As noted by other answers and commenters, as of Java 8 you can simply call Map#getOrDefault(...).

[Original]

There's no Map implementation that does this exactly but it would be trivial to implement your own by extending HashMap:

public class DefaultHashMap<K,V> extends HashMap<K,V> {
  protected V defaultValue;
  public DefaultHashMap(V defaultValue) {
    this.defaultValue = defaultValue;
  }
  @Override
  public V get(Object k) {
    return containsKey(k) ? super.get(k) : defaultValue;
  }
}