Marcin Luckner Warsaw University of Technology Faculty of Mathematics and Information Science

Transcription

1 Marcin Luckner Warsaw University of Technology Faculty of Mathematics and Information Science

2 } Annotations do not directly affect program semantics. } May be recognized by tools and libraries which could change behavior. } Annotations may be read from source files, class files or by reflection at run time. 2

3 a method is intended to override a method in a superclass. a class or a method may be indicated as not to be used any more (generates compiler warning if used). turns of certain warnings from a compiler deprecation, unchecked, fallthrough, path, serial,finally, 3

4 } Annotations with many parameters must be called with parameters names } A single parameter named value may be shortened in use. 4

5 } Annotations are created with specialized syntax similar to interfaces. } Each method declaration defines an element of the annotation type. } Method declaration must not have any parameters or a throws clause. } Return types are restricted to primitives, String, Class, enums and arrays of preceding types. } Methods can have defaults values. 5

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7 whether the annotations are available SOURCE, CLASS, RUNTIME defines where you can apply this annotation METHOD, PARAMETER, CONSTRUCTOR, LOCAL VARIABLE, ANNOTATION TYPE, PACKAGE 7

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9 /* This is a comment * that continues * across lines */ /* This is a comment that continues across lines */ // This is a one-line comment 9

10 /** A class comment */ public class Documentation1 { /** A field comment */ public int i; /** A method comment */ public void f() {} } 10

11 /** * You can <em>even</em> insert a list: * <ol> * <li> Item one * <li> Item two * <li> Item three * </ol> */ 11

12 This tag allows you to refer to the documentation in other fully-qualified-classname#method-name } {@link package.class#member label} can be used inline as the hyperlink text } {@docroot} the relative path to the documentation root directory } {@inheritdoc} Inherits the documentation from the nearest base class 12

13 } author-information indicate the version of this code that began using a particular feature. 13

14 } parameter-name description parameter-name the identifier in the method parameter list, description text that can continue on subsequent description description gives you the meaning of the return value. 14

15 } fully-qualified-class-name description fully-qualified-class-name gives an unambiguous name of an exception class description tells you why this particular type of exception can emerge from the method call. indicate features that were superseded by an improved feature 15

16 /** The first Thinking in Java example program. * Displays a string and today s date. Bruce Eckel */ public class HelloDate { /** Entry point to class & application. args array of string arguments exceptions No exceptions thrown */ public static void main(string[] args) { System.out.println("Hello, it s: "); System.out.println(new Date()); } } /* Output: (55% match) Hello, it s: Wed Oct 05 14:39:36 MDT 2005 */ 16