Check if a class extends another at Runtime : Java

Summary :

• If you want to know whether or not a Class extends another, use Class#isAssignableFrom(Class)
• Class#isAssignableFrom(Class) also returns true if both classes are same
• To find if an object is instance of a class use instanceof operator
• To know if a class is direct sub class of another class then use Class#getSuperClass().equals(Class)

Setup :

We have an interface MyInterface and three classes MyBaseClass, MySubClass and SomeOtherClass with the below hierarchy.

interface MyInterface {
}

class MyBaseClass implements MyInterface {
}

class MySubClass extends MyBaseClass {
}

class SomeOtherClass {
}   

Tests:

   

public class Test {
  
  public static void main( String[] args ) {
    
    /*
     * Checking if a class is same as or is a superclass or superinterface
     * 
     * of another class (the class in parameter)
     */
    System.out.println( MyBaseClass.class.isAssignableFrom( MyBaseClass.class ) );// true : same class
    System.out.println( MyBaseClass.class.equals( MyBaseClass.class ) );// true : same class
    System.out.println( MyBaseClass.class.isAssignableFrom( MySubClass.class ) );// true : superclass
    System.out.println( MyInterface.class.isAssignableFrom( MySubClass.class ) );// true : superinterface
    System.out.println( MyBaseClass.class.isAssignableFrom( SomeOtherClass.class ) );// false : the two classes has no relation
    System.out.println( MySubClass.class.isAssignableFrom( MyBaseClass.class ) );// false : MySubClass is not the superclass
    
    /*
     * Checking if a object is instance of a class
     */
    
    IMyInterface object = new MyBaseClass( );
    System.out.println( object instanceof MyInterface ); // true
    System.out.println( object instanceof MyBaseClass ); // true
    System.out.println( object instanceof MySubClass ); // false
    System.out.println( object instanceof SomeOtherClass );// false
    
    /*
     * check if a class is direct superclass of another
     */
    
    System.out.println( MySubClass.class.getSuperclass( ).equals( MyInterface.class ) );// false : its not a directsuper class, interface
    System.out.println( MyBaseClass.class.getSuperclass( ).equals( MyInterface.class ) );// false : its not a directsuper class, interface
    System.out.println( MySubClass.class.getSuperclass( ).equals( MyBaseClass.class ) );// true : MyBaseClass is extending MySubClass
  }
}
   

Full code :

   

public class Test {
  
  public static void main( String[] args ) {
    
    /*
     * Checking if a class is same as or is a superclass or superinterface
     * 
     * of another class (the class in parameter)
     */
    System.out.println( MyBaseClass.class.isAssignableFrom( MyBaseClass.class ) );// true : same class
    System.out.println( MyBaseClass.class.equals( MyBaseClass.class ) );// true : same class
    System.out.println( MyBaseClass.class.isAssignableFrom( MySubClass.class ) );// true : superclass
    System.out.println( MyInterface.class.isAssignableFrom( MySubClass.class ) );// true : superinterface
    System.out.println( MyBaseClass.class.isAssignableFrom( SomeOtherClass.class ) );// false : the two classes has no relation
    System.out.println( MySubClass.class.isAssignableFrom( MyBaseClass.class ) );// false : MySubClass is not the superclass
    
    /*
     * Checking if a object is instance of a class
     */
    
    IMyInterface object = new MyBaseClass( );
    System.out.println( object instanceof MyInterface ); // true
    System.out.println( object instanceof MyBaseClass ); // true
    System.out.println( object instanceof MySubClass ); // false
    System.out.println( object instanceof SomeOtherClass );// false
    
    /*
     * check if a class is direct superclass of another
     */
    
    System.out.println( MySubClass.class.getSuperclass( ).equals( MyInterface.class ) );// false : its not a directsuper class, interface
    System.out.println( MyBaseClass.class.getSuperclass( ).equals( MyInterface.class ) );// false : its not a directsuper class, interface
    System.out.println( MySubClass.class.getSuperclass( ).equals( MyBaseClass.class ) );// true : MyBaseClass is extending MySubClass
  }
}

interface MyInterface {
}

class MyBaseClass implements MyInterface {
}

class MySubClass extends MyBaseClass {
}

class SomeOtherClass {
}