java.lang.Class類的getDeclaredAnnotationsByType()方法用於獲取存在於此類中的指定聲明注釋類型的聲明注釋。該方法為指定的聲明的注釋類型返回聲明的注釋的數組。
用法:
public A[] getDeclaredAnnotationsByType(Class<T> declared annotationClass)
參數:此方法接受一個聲明的注釋類型的參數,該參數是要獲取的聲明注釋的類型。
返回值:此方法為指定的聲明的注釋類型返回聲明的注釋的數組。
異常:該方法拋出:
- NullPointerException :如果給定的聲明注釋類為null。
下麵的程序演示了getDeclaredAnnotationsByType()方法。
範例1:
// Java program to demonstrate
// getDeclaredAnnotationsByType() method
import java.util.*;
import java.lang.annotation.*;
// create a custom DeclaredAnnotation
@Retention(RetentionPolicy.RUNTIME)
@interface DeclaredAnnotation {
// This declared annotation has two attributes.
public String key();
public String value();
}
// call DeclaredAnnotation for method
// and pass values for declared annotation
@DeclaredAnnotation(key = "GFG", value = "GeeksForGeeks")
public class Test {
public Object obj;
public static void main(String[] args)
throws ClassNotFoundException
{
// returns the Class object for this class
Class myClass = Test.class;
System.out.println(
"Class represented by myClass:"
+ myClass.toString());
// Get the declared annotation
// using getDeclaredAnnotationsByType() method
System.out.println(
"DeclaredAnnotation of myClass of type DeclaredAnnotation:"
+ Arrays.toString(
myClass
.getDeclaredAnnotationsByType(
DeclaredAnnotation.class)));
}
}
輸出:
Class represented by myClass:class Test
DeclaredAnnotation of myClass of type DeclaredAnnotation:[@DeclaredAnnotation(key=GFG, value=GeeksForGeeks)]
範例2:
// Java program to demonstrate
// getDeclaredAnnotationsByType() method
import java.util.*;
import java.lang.annotation.*;
@Deprecated
public class Test {
public Object obj;
public static void main(String[] args)
throws ClassNotFoundException
{
try {
// returns the Class object for this class
Class myClass = Test.class;
System.out.println(
"Class represented by myClass:"
+ myClass.toString());
// Get the declared annotation
// using getDeclaredAnnotationsByType() method
System.out.println(
"DeclaredAnnotation of myClass of type Deprecated:"
+ Arrays.toString(
myClass
.getDeclaredAnnotationsByType(
Deprecated.class)));
}
catch (Exception e) {
System.out.println(e);
}
}
}
輸出:
Class represented by myClass:class Test
DeclaredAnnotation of myClass of type Deprecated:[@java.lang.Deprecated()]
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注:本文由純淨天空篩選整理自srinam大神的英文原創作品 Class getDeclaredAnnotationsByType() method in Java with Examples。非經特殊聲明,原始代碼版權歸原作者所有,本譯文未經允許或授權,請勿轉載或複製。