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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methods Help is the obvious If you don’t like frames, you can choose NO FRAMES • Deprecated methods are those that have been replaced by better methods and should not be used The main information area • • • • • • • General description of the class Field summary • In each case, the Constructor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