super() in constructor

Question

I'm reading through some code. In the constructor it has super() but the class implements interface which of course doesn't have a constructor. So which super() it is referring to?

public class BoundingBox implements IBoundingVolume {  public BoundingBox() {         super();         mTransformedMin = new Number3D();         mTransformedMax = new Number3D();         mTmpMin = new Number3D();         mTmpMax = new Number3D();         mPoints = new Number3D[8];         mTmp = new Number3D[8];         mMin = new Number3D();         mMax = new Number3D();         for(int i=0; i<8; ++i) {             mPoints[i] = new Number3D();             mTmp[i] = new Number3D();         } }   public interface IBoundingVolume {     public void calculateBounds(Geometry3D geometry);     public void drawBoundingVolume(Camera camera, float[] projMatrix, float[] vMatrix, float[] mMatrix);     public void transform(float[] matrix);     public boolean intersectsWith(IBoundingVolume boundingVolume);     public BaseObject3D getVisual(); } 

Answer 1

super() refers to the extended class (not an implemented interface). Which in this case is Object

So it will call the constructor in Object (Which does nothing)

Answer 2

Super is referencing to the extended class. By default it is the Object class. The constructor in Object does nothing. In other words you can delete this line as it is not necessary.

Please also note what Oracle is saying about this topic:

If a constructor does not explicitly invoke a superclass constructor, the Java compiler automatically inserts a call to the no-argument constructor of the superclass. If the super class does not have a no-argument constructor, you will get a compile-time error. Object does have such a constructor, so if Object is the only superclass, there is no problem.

Source: http://docs.oracle.com/javase/tutorial/java/IandI/super.html