I do not see methods in the API documentation.
Where did you look with that link?
There two ways to get to a method's doc:
1)Click on INDEX in the top blue Navigation bar
Select first letter of the method
A list of all the methods with that first letter will be displayed.
Find the method in the class that you are interested in.
2) Find the class in the lower lefthand frame
Click on the name of the class
All the documentation for that class will be shown in the main frame.
Read the various sections for that class
hasNextBoolean is a method used to check if the next token can be interpreted as a boolean value.
nextBoolean is a method which is used to scan the next token of the input into a boolean value and returns that value.
In other words:
has... checks if the next token is a valid value: returns True or false
next.. reads and returns the next value: returns the value