question: public boolean contains ( long prefix_hash ) { if ( prefix_hash == 0 ) { return false ; } int idx = - 1 * Arrays . binarySearch ( hashes_idx , prefix_hash ) - 1 ; if ( idx == cache_size ) { return false ; } else { return ( hashes_idx [ idx ] & PREFIX_HASH_MASK ) == prefix_hash ; } }
target:  Checks if there are any object in the cache generated on the base of encoding with prefix corresponding to the specified hash code.