New to Java

I am trying to understand how to read the Java API. I have bought Oracle's Books "Java The Complete Reference" and "Java A Beginners Guide" but am still unsure how to read the API.

Let me clarify what I'm asking to avoid confusion.

The class java.util.ProcessBuilder http://download.oracle.com/javase/7/docs/api/

Has a Constructor section that lists
Constructor and Description
ProcessBuilder(List<String> command)
Constructs a process builder with the specified operating system program and arguments.
ProcessBuilder(String... command)
Constructs a process builder with the specified operating system program and arguments.

How do I read the ProcessBuilder(List<String> command) so that I can understand it and implement its use?

Later when it talks about methods such as List<String> command()
Returns this process builder's operating system program and arguments.
How do I understand this and make use of the method?

Is it possible for this to be explained to cover the whole API so that when a class is looked up the constructor and methods are explained that someone who does not understand can take any class and have the constructor and methods from the API and know how to implement them?

Thank you
FtroopSon