Java Class getDeclaredClasses() Method

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Description

The Java Class getDeclaredClasses() method returns an array of Class objects including public, protected, default (package) access, and private classes and interfaces declared by the class, but excludes inherited classes and interfaces.

This method returns an array of length 0 if the class declares no classes or interfaces as members, or if this Class object represents a primitive type, an array class, or void.

Declaration

Following is the declaration for java.lang.Class.getDeclaredClasses() method

public Class<?>[] getDeclaredClasses() throws SecurityException

Parameters

NA

Return Value

This method returns the array of Class objects representing all the declared members of this class.

Exception

SecurityException − If a security manager, s, is present.

Getting All the Declared Classes Example

The following example shows the usage of java.lang.Class.getDeclaredClasses() method. In this program, the class of the ClassDemo is retrieved using forName() method. Using getDeclaredClasses(), we've retrieved inner classes declared inside ClassDemo class.

package com.tutorialspoint;

public class ClassDemo {

   public static void main(String[] args) {
 
      try {
         // returns the Class object associated with this class
         Class cls = Class.forName("ClassDemo");

         /* returns the array of Class objects representing all the declared 
            members of this class */
         Class[] classes = cls.getDeclaredClasses();
         for (int i = 0; i < classes.length; i++) {
            System.out.println("Class = " + classes[i].getName());
         }
      } catch (ClassNotFoundException e) {
         System.out.println(e.toString());
      }
   }

   public class InnerClass1 {
      public InnerClass1() {
         System.out.println("Inner Class1");
      }
   }

   public class InnerClass2 {
      public InnerClass2() {
         System.out.println("Inner Class2");
      }
   }

   private class InnerPrivateClass {
      public InnerPrivateClass() {
         System.out.println("Inner Private Class");
      }
   }
} 

Output

Let us compile and run the above program, this will produce the following result −

Class = ClassDemo$InnerPrivateClass
Class = ClassDemo$InnerClass2
Class = ClassDemo$InnerClass1

Getting All the Declared Classes of ArrayList Example

The following example shows the usage of java.lang.Class.getDeclaredClasses() method. In this program, the class of the ArrayList is retrieved using class property. Using getDeclaredClasses(), we've retrieved inner classes declared inside ClassDemo class.

package com.tutorialspoint;

import java.util.ArrayList;

public class ClassDemo {

   public static void main(String[] args) {

      // returns the Class object associated with this class
      Class cls = ArrayList.class;

      /* returns the array of Class objects representing all the declared 
         members of this class */
      Class[] classes = cls.getDeclaredClasses();
      for (int i = 0; i < classes.length; i++) {
         System.out.println("Class = " + classes[i].getName());
      }
   }
} 

Output

Let us compile and run the above program, this will produce the following result −

Class = java.util.ArrayList$ListItr
Class = java.util.ArrayList$Itr
Class = java.util.ArrayList$SubList
Class = java.util.ArrayList$ArrayListSpliterator

Getting All the Declared Classes of Thread Example

The following example shows the usage of java.lang.Class.getDeclaredClasses() method. In this program, the class of the Thread is retrieved using class property. Using getDeclaredClasses(), we've retrieved inner classes declared inside ClassDemo class.

package com.tutorialspoint;

public class ClassDemo {

   public static void main(String[] args) {

      // returns the Class object associated with this class
      Class cls = Thread.class;

      /* returns the array of Class objects representing all the declared 
         members of this class */
      Class[] classes = cls.getDeclaredClasses();
      for (int i = 0; i < classes.length; i++) {
         System.out.println("Class = " + classes[i].getName());
      }
   }
} 

Output

Let us compile and run the above program, this will produce the following result −

Class = java.lang.Thread$FieldHolder
Class = java.lang.Thread$ThreadIdentifiers
Class = java.lang.Thread$Constants
Class = java.lang.Thread$ThreadNumbering
Class = java.lang.Thread$UncaughtExceptionHandler
Class = java.lang.Thread$State
Class = java.lang.Thread$Caches
Class = java.lang.Thread$Builder