question: protected String internalPut ( String key , String newValue ) { synchronized ( childAndPropertyLock ) { String oldValue = properties . get ( key ) ; if ( oldValue != null && oldValue . equals ( newValue ) ) return oldValue ; properties = properties . put ( key , newValue ) ; return oldValue ; } }
target:  Stores the given (key,value) pair, performing lazy initialization of the properties field if necessary. Returns the old value for the given key, or null if no value existed.