this is a reference to the object on which behalf the current method was invoked. this(anything) is an invocation of constructor. this is a keyword in Java, it means its current instance of the class. this(“stackoverflow”) is calling constructor in the class which will be a overloaded call.
For More Information Please Refer: https://stackoverflow.com/questions/28718973/what-are-the-differences-between-this-and-this-in-java