Java 中的类 getDeclaredField()方法，带示例
原文:https://www . geesforgeks . org/class-getdeclaredfield-method-in-Java-with-examples/
Java . lang . class的 getDeclaredField() 方法用于获取该类的指定字段。方法以字段对象的形式返回此类的指定字段。
语法:
public Field getDeclaredField(String fieldName)
throws NoSuchMethodException,
SecurityException
参数:该方法接受一个参数字段名，即要获取的字段。
返回值:该方法以 field 对象的形式返回该类的指定字段。
异常此方法抛出:
- 如果找不到具有指定名称的字段，则 NoSuchFieldException 。
- 空指针异常如果名称为空
-
SecurityException if a security manager is present and the security conditions are not met.
下面的程序演示了 getDeclaredField()方法。
例 1:
```java // Java program to demonstrate // getDeclaredField() method
import java.util.*;
public class Test {
public Object obj;
public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
// returns the Class object for this class Class myClass = Class.forName("Test");
System.out.println("Class represented by myClass: " + myClass.toString());
String fieldName = "obj";
// Get the field of myClass // using getDeclaredField() method System.out.println( fieldName + " Field of myClass: " + myClass.getDeclaredField(fieldName)); } } ```
Output:
```java Class represented by myClass: class Test obj Field of myClass: public java.lang.Object Test.obj
```
例 2:
```java // Java program to demonstrate // getDeclaredField() method
import java.util.*;
class Main {
private Object obj;
public static void main(String[] args) throws ClassNotFoundException, NoSuchFieldException {
// returns the Class object for this class Class myClass = Class.forName("Main");
System.out.println("Class represented by myClass: " + myClass.toString());
String fieldName = "obj";
try { // Get the field of myClass // using getDeclaredField() method System.out.println( fieldName + " Field of myClass: " + myClass.getDeclaredField(fieldName)); } catch (Exception e) { System.out.println(e); } } } ```
Output:
```java Class represented by myClass: class Main obj Field of myClass: private java.lang.Object Main.obj
```
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