e412. creating a preference node.txt

这里面包含了一百多个JAVA源文件

The methods used to create a preference node are identical to the ones for retrieving a preference node. When retrieving a preference node, the preference node is automatically created if it doesn't exist. In fact, when you retrieve a node, you can't tell if it was just created or not. 
See e413 Retrieving a Preference Node for an example of retrieving preference nodes. 

See also e415 Determining If a Preference Node Exists.