question: @ Override public boolean containsKey ( Object key ) { if ( key == null ) { return entryForNullKey != null ; } int hash = key . hashCode ( ) ; hash ^= ( hash > > > 20 ) ^ ( hash > > > 12 ) ; hash ^= ( hash > > > 7 ) ^ ( hash > > > 4 ) ; HashMapEntry < K , V > [ ] tab = table ; for ( HashMapEntry < K , V > e = tab [ hash & ( tab . length - 1 ) ] ; e != null ; e = e . next ) { K eKey = e . key ; if ( eKey == key || ( e . hash == hash && key . equals ( eKey ) ) ) { return true ; } } return false ; }
target:  Returns whether this map contains the specified key.