Null vs Marker Interface

Null interface is just another name for Marker Interface or the other way round. They are used interchangeably as far as I know.

These are just interface with no methods in them. Examples of marker interfaces are : Serializable, Cloneable.

Null interface is another name for marker interface. Such an interface is empty, i.e. without any method declarations.

For example Serializable, Cloneable class in java. In earlier versions of Java, Marker Interfaces were the only way to declare metadata about a class