get(Object key) Returns the value to which the key is mapped in this identity hash map, or null if the map contains no mapping for this key.

download.oracle.com/java...

看樣子該libray包含了Hash Map的key/value pair.. 沒有就回傳null, 但不會顯示錯誤...

trace code到第五層才發現...這那門子coding阿!!