Class getDeclaredField() method in Java with Examples

The getDeclaredField() method of java.lang.Class class is used to get the specified field of this class. The method returns the specified field of this class in the form of Field object.

Syntax:

public Field getDeclaredField(String fieldName)
       throws NoSuchMethodException,
              SecurityException

Parameter: This method accepts a parameter fieldName which is the Field to get.

Return Value: This method returns the specified field of this class in the form of Field objects.

Exception This method throws:

• NoSuchFieldException if a field with the specified name is not found.
• NullPointerException if name is null
• SecurityException if a security manager is present and the security conditions are not met.

  Below programs demonstrate the getDeclaredField() method.

  Example 1:

  // 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:

  Class represented by myClass: class Test
  obj Field of myClass: public java.lang.Object Test.obj
  

  Example 2:

  // 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:

  Class represented by myClass: class Main
  obj Field of myClass: private java.lang.Object Main.obj
  

  Reference: https://docs.oracle.com/javase/9/docs/api/java/lang/Class.html#getDeclaredField-java.lang.String-