Question

I have an application which is written in Java. I have 3 classes mysql_query, tablesetup, table_action. Now inside the class of each of the class I have created the object of other classes which results in recursive object invocation. What are the alternative that I can use to fix this problem ?

For Example:

In mysql_query.java i have

public class mysql_query{  
   tablesetup tablesetup = new tablesetup();  
   table_action table_action = new table_action();   
}

In tablesetup.java I have

public class tablesetup{  
   mysql_query mysql_query= new mysql_query();  
   table_action table_action = new table_action();   
}

Similarly in table_action.java I have

public class table_action{  
   mysql_query mysql_query= new mysql_query();  
   tablesetup tablesetup= new tablesetup();   
}

–EDIT–
passing one class object to the constructor of other will not workout in my case as I have many dependent classes like this. So usually how programmers arrange these classes ? Can I use interface ? Is it appropriate to use in this case ?

Answer 1

• in tablesetup you are instantiating a table_action
• in table_action you are instantiating a tablesetup

I guess you see the loop – the first creates a new instance of the second which creates a new instance of the first, which creates a new instance of the second, and so on until your stack (holding method and constructor calls) is filled.

A little more clarification – when you instantiate an object through its constructor, all of its fields are initialized. So when you instantiate table_action, new tablesetup() is invoked in order to initialize the tablesetuptablesetup variable.

Circular dependencies are not a good thing, but you can have them. You just need to pass a reference to an existing tablesetup when creating table_actions.

Apart from that – you are not using proper java naming. You should not use lowercase classes and underscores. The proper names are TableSetup, TableAction and MySQLQuery. Same goes for variable names, apart from the upper-case. They should by mysqlQuery, tableSetup, etc.