Transcript Using the Java API

Using the Java API
http://java.sun.com/j2se/1.3/docs/api/
Where’s the API?
Overview
General approach
• If you know the name of the package, click it in the
upper left panel; or click All Classes
• Click on the class in the lower left panel
• Scroll in the right pane to find the summary of the
field, method, or constructor you want
– Or just read the general description
• For more information, click the link in the
summary to go to the detailed information
The Packages panel
• Choose the package you are
interested in
• Or, choose All Classes
• Classes in java.lang are
automatically imported into
every program--you don’t
have to do it yourself
The Classes panel
• This panel shows both
classes and interfaces
• We haven’t yet talked about
interfaces
• Note that some classes have
names similar to primitive
types (Boolean, Byte,
Character)
The links bar
•
•
•
•
Overview is where you start out
Index is handy for looking up methods
Help is the obvious
If you don’t like frames, you can choose
NO FRAMES
• Deprecated methods are those that have been
replaced by better methods and should not be used
The main information area
•
•
•
•
•
•
•
General description of the class
Field summary
• In each case, the
Constructor summary
“summary” is the first
Method summary
sentence of the “detail”
Field detail
Constructor detail
Method detail
Reading the method descriptions I
• An example from the String class:
– public char charAt(int index)
• Returns the character at the specified index
–
–
–
–
–
–
public means accessible from anywhere
char is the return type
charAt is the name of the method
int is the type of parameter expected
index is just a suggestive name
Example use: char firstChar = myStr.charAt(0);
Reading the method descriptions II
• Another example from the String class:
– public static String valueOf(int i)
• Returns the string representation of the int argument.
–
–
–
–
–
–
public means accessible from anywhere
static means this is a class method (see use below)
String is the return type, and is a hyperlink
valueOf is the name of the method
int is the type of parameter expected
i is just a suggestive name
– Example use: String numeral = String.valueOf(m / n);
How was this documentation
produced?
• All Java documentation was produced by the
javadoc program from javadoc (or just doc)
comments in the source code
• Your doc comments can be used in the same way
to produce professional-looking documentation
• The Interface menu item in BlueJ does the same
basic thing as javadoc
– Like most things in BlueJ, fancy features have
been omitted in the interests of simplicity
Value of the API
• Version
packages
classes
methods
Java 1.0
8
212
1545
Java 1.1
23
504
3851
Java 1.2
60
1781
15060
Java 1.3
77
2130
17158
Java .14
?
?
?
• You can only learn a small fraction of these
• When you learn the kinds of things that are in the API, and
learn to find your way around in it, you become a far more
effective and efficient programmer
• A good craftsman knows his/her tools
The End