類類isAnnotationPresent()方法 (Class class isAnnotationPresent() method)

• isAnnotationPresent() method is available in java.lang package.

  isAnnotationPresent()方法在java.lang包中可用。

• isAnnotationPresent() method returns true when the annotation for the given type exists on this entity otherwise it returns false.

  當給定類型的注釋存在于此實體上時， isAnnotationPresent()方法將返回true，否則將返回false。

• isAnnotationPresent() method is a non-static method, it is accessible with the class object only and if we try to access the method with the class name then we will get an error.

  isAnnotationPresent()方法是一個非靜態方法，僅可通過類對象訪問，如果嘗試使用類名訪問該方法，則會收到錯誤消息。

• isAnnotationPresent() method: may throw an exception at the time checking present annotation.

  isAnnotationPresent()方法 ：在檢查當前注釋時可能會引發異常。

  NullPointerException: In this exception, when the given annotation class is null.

  NullPointerException ：在此異常中，當給定的注釋類為null時。

Syntax:

句法：

public boolean isAnnotationPresent(Class ann_class);

Parameter(s):

參數：

• Class ann_class – represents the Class object similar or correspondent to the annotation type.

  類ann_class –表示與注釋類型相似或對應的Class對象。

Return value:

返回值：

The return type of this method is boolean, it returns a boolean value based on the following cases,

此方法的返回類型為boolean ，它基于以下情況返回布爾值：

• It returns true, when an annotation for the given type exists on this entity.

  當給定類型的注釋存在于此實體上時，它返回true 。

• It returns false, when an annotation for the given type does not exists.

  當給定類型的注釋不存在時，它返回false 。

Example:

例：

// Java program to demonstrate the example // of boolean isAnnotationPresent(Class ann_class) method of Class import java.security.*; public class IsAnnotationPresentOfClass {public static void main(String[] args) throws Exception {Class ann1 = Identity.class;Class ann2 = Deprecated.class;// We are checking Annotation Present type of Deprecated //class by using the method isAnnotationPresent()boolean b1 = ann2.isAnnotationPresent(ann2);System.out.println("is Deprecated an Annotation Present type" + " " + b1);// We are checking Annotation Present type of Identity class// by using the method isAnnotationPresent()boolean b2 = ann1.isAnnotationPresent(ann1);System.out.println("is Deprecated an Annotation Present type" + " " + b2);} }

Output

輸出量

is Deprecated an Annotation Present type false is Deprecated an Annotation Present type false

翻譯自: https://www.includehelp.com/java/class-class-isannotationpresent-method-with-example.aspx

總結

以上是生活随笔為你收集整理的Java类class isAnnotationPresent（）方法与示例的全部內容，希望文章能夠幫你解決所遇到的問題。

如果覺得生活随笔網站內容還不錯，歡迎將生活随笔推薦給好友。