java.lang.Package類的isAnnotationPresent()方法用於檢查此類中是否存在指定注釋類型的注釋。該方法返回一個聲明相同的布爾值。
用法:
public boolean isAnnotationPresent(Class<T> annotationClass)
參數:此方法接受參數注釋類,它是要獲取的注釋的類型。
返回值:此方法返回聲明相同的布爾值。
異常:該方法拋出:
- NullPointerException :如果給定的注釋類為null。
下麵的程序演示了isAnnotationPresent()方法。
範例1:
// Java program to demonstrate
// isAnnotationPresent() method
import java.util.*;
import java.lang.annotation.*;
// create a custom Annotation
@Retention(RetentionPolicy.RUNTIME)
@interface Annotation {
// This annotation has two attributes.
public String key();
public String value();
}
// call Annotation for method
// and pass values for annotation
@Annotation(key = "GFG", value = "GeeksForGeeks")
public class Test {
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());
// Check if there is any annotation
// using isAnnotationPresent() method
System.out.println(
"If there is any annotation in myClass:"
+ myClass.isAnnotationPresent(
Annotation.class));
}
}
輸出:
Class represented by myClass:class Test
If there is any annotation in myClass:true
範例2:
// Java program to demonstrate
// isAnnotationPresent() method
import java.util.*;
import java.lang.annotation.*;
// Class with no annotations
public class Test {
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 annotation
// using isAnnotationPresent() method
System.out.println(
"If there is any annotation in myClass:"
+ myClass.isAnnotationPresent(
Annotation.class));
}
}
輸出:
Class represented by myClass:class Test
If there is any annotation in myClass:false
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注:本文由純淨天空篩選整理自guptayashgupta53大神的英文原創作品 Package isAnnotationPresent() 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。