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javaooparchitecturesolid-principles

How to populate a list of interfaces?

I am fairly new to the SOLID principles and I have found i often come to the following situation.

I have an implementation of a task that is tied to an interface, when i need to use the class i just use DI for such an interface.

My problem is what to do when i need multiple implementations, for example.

List<IDataSource> dataSources = new ArrayList<IDataSource>();
dataSources.add(new DataSourceOne());
dataSources.add(new DataSourceTwo());
.... and so one...

then later i will loop over the array to action the interface method for each implementation.

Is this bad practice? is there a way of populating the list without the new keyword? eg c# reflection. or is the a design pattern that avoids this?

Solution

  • What have you got against the new keyword when you want to create a new object?

    You can simplify the code as:

    List<DataSource> dataSources = Array.asList(
    new DataSourceOne(),
    new DataSourceTwo(),
    ...
);

    Although it has some uses, using reflection is almost always a really bad idea.