|
|
| Java Developers Desk: Annotations |
|
Usage:
@Example (“Hi ! How r you”)
public void anymethod(){
————
} |
Multi-value or Full-value
These types of annotations can have multiple
data members. Therefore use full value
annotations to pass the values to all the data
members.
Example:
public @interface Example{
String showSomething();
int num;
String name;
} |
Usage:
@Example (showSomething = “Hi! How r
you”, num=5, name=”amit” )
public void anymethod{
// code here
} |
Rules defining the Annotation type:
Here are some rules that one should follow
while defining and using annotations types
- Start the annotation declaration starting
with the symbol “at” @ following the
interface keyword that should follow the
annotation name.
- Method declaration should not throw
any exception.
- Method declaration should not contain
any parameter.
- Method using annotations should return
a value, one of the types given below:
- String
- primitive
- enum
- Class
- array of the above types
|
|
Categorizing Annotations:
JDK 5 contains two categories of
annotations:
Simple annotations:
These types of annotations are used to
annotate the code only. We can not use
these types of annotations for creating the
custom annotation type.
Meta annotations:
Also known as annotations of annotations
are used to annotate the annotation-type
declaration.
I. Simple annotations:
JDK 5 includes three types of simple
annotations.
- Override
- Depricated
- Suppresswarning
JDK 5 does not include many built-in
annotations but it facilitates to core java to
support annotation features. Now will discuss
in brief each of the above simple annotation
types along with examples.
1) Override annotation:
The override annotation ensures that the
annotated method is used to override the
method in the super class. If the method
containing this type of annotation does not
override the method in the super class then
the compiler will generate a compile time error.
Lets take an example and demonstrate what
will happen if the annotated method does not
override the method in the super class.
Example 1:
public class Override_method{
@Override
public String toString(){
return super.toString() +
“Will generate an compile time error.”;
}} |
|
|
|
Jan 2008 | Java Jazz Up | 8 |
| |
|
| |
| View All Topics |
| All Pages of this Issue |
Pages:
1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
11,
12,
13,
14,
15,
16,
17,
18,
19,
20,
21,
22,
23,
24,
25,
26,
27,
28,
29,
30,
31,
32,
33,
34,
35,
36,
37,
38,
39,
40,
41,
42,
43,
44,
45,
46,
47,
48,
49,
50,
51,
52,
53 ,
54,
55,
56,
57,
58,
59,
60,
61,
62,
63 ,
64,
65 ,
66 ,
67 ,
68 ,
69 ,
70 ,
71 ,
72 ,
73 ,
74 ,
75 ,
76 ,
77 ,
78 ,
79 ,
80 ,
81 ,
82 ,
83,
84 ,
85 ,
86,
87 ,
88,
89 ,
90 ,
91 ,
92 ,
93 ,
94 ,
95 ,
96 ,
97 ,
98 ,
99 ,
100 ,
101 ,
102 ,
103,
104 ,
105 ,
106,
107,
Download PDF |
|
|
|
|
|
|
| |
| |
|
