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;
  }
}

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 ; } }
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 .
