Transcript Using the API

Using the Java API
http://java.sun.com/j2se/1.3/docs/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
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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• Deprecated methods are those that have been
replaced by better methods and should not be used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
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General description of the class
Field summary
• In each case, the
“summary” is the
Constructor summary
first sentence of the
Method summary
“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
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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.
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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
• Java 1.2 gives you 60 packages containing
1781 classes and interfaces, 3538 fields, 2337
constructors, and 15060 methods
• 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