unfamilier java syntax

[jazy smith]

Hi all,

I recently came across the below java code for getList(). can anyone help me debugging it. I can't understand the syntax. if anyone have simple example of such syntax, I'd be obliged.

public class MockClass
{

    public static ContractItem getContractItem() 
   {
        ContractItem contract = new ContractItem();              
        return contract;
    };
     
    public static void getList() 
    {        

        ArrayList<ContractItem> contractlist = new ArrayList<ContractItem>() 
        {
         {
            
            contract = getContractItem();
            contract.setProduct();
            add(contract);
            
            contract = getContractItem();
            contract.setProduct();
            add(contract);
         }
        };

      
     }

}
    	
    	

[Wouter Oet]

That code doesn't compile. But with some changes it could be a anonymous class with an initializer block.

[Ralph Cook]

Please elaborate on what your question is. The method looks fine to me.

What is it that confuses you? I hope we can assume you are familiar with equals signs (=), braces ({}), and some other basics. Are you confused by the angle brackets? the 'static' in the declaration?

Are you sure it is the syntax that bothers you?

It really helps to have an actual question...

rc

[Manjula Weerasinghe]

It (in line 13) is an anonymous inner class with instance init block. But your code does not compile it has other errors.
Since this inner class is declared in a static method, you need to define your "contract" variable as a static variable.

        ArrayList<ContractItem> contractlist = new ArrayList<ContractItem>() // start of anonymous inner class which extends ArrayList<ContractItem>
        {
         { // instance init block
            
            contract = getContractItem();// is there any static variable named "contract" belong to MockClass class ?
            contract.setProduct();
            add(contract);
            
            contract = getContractItem();
            contract.setProduct();
            add(contract);
         }
        };

[Rob Spoor]

It doesn't need to be static; it can also be a) a final local variable or final parameter in the method, or b) an instance variable of the enclosing class (or the enclosing class' enclosing class if that exists, etc).

[Manjula Weerasinghe]

Rob Spoor wrote:It doesn't need to be static; it can also be a) a final local variable or final parameter in the method, or b) an instance variable of the enclosing class (or the enclosing class' enclosing class if that exists, etc).

Hi Rob,

Since "contract" variable is reassigned several times to different objects in this example, you cannot use a final local variable or final method parameter inside the inner class as the "contract" variable. But you may use any other final local variable or a final method parameters inside the inner class as long as you keep the meaning of the "final" modifier (not reassigning it to a different value/reference).

Since this inner class has defined inside a "static" method, you can only access the static variables of the enclosing class (I am not very good at English, but as I know this means outer class (MockClass), correct me if I am wrong) and you cannot access the instance variables of the enclosing class, because there is no reference to "this" (current object) inside a static method.

Thanks & Regards,
Manjula

[Rob Spoor]

You're absolutely right. I missed the static part, and overlooked the assignments. So yes, you're right, contract must be a static field of one of the enclosing classes.