Unchecked warning

[anjibman]

Hi All,

I didn't get what this warning message means and how to correct this.

warning: [unchecked] unchecked conversion

I have following components and codes:
a) Interface

public interface MyInterface {
    
    public List findAll();
    
}

b) Implementation Class

public class MyClass implements MyInterface{

    public List findAll() {
        List<MyData> result = new ArrayList<MyData>();
        result.add(new MyData("1","ABC"));
        result.add(new MyData("12","DEF"));
        result.add(new MyData("13","GHI"));
        result.add(new MyData("14","JKL"));
        result.add(new MyData("15","MNO"));       
        return result;
    }
    
}

c) Main Class

public class MainClass {
    
    public static void main(String[] args) {
        MyClass test = new MyClass();
        List<MyData> data = new ArrayList<MyData>();
        data = test.findAll();        
    }    
}

I am getting this warning in line 6 of Main Class. Can any one suggest how I can avoid this message?

Thanks

[doWhile]

The interface MyInterface defines a method that returns a List, but there is no type definition of what the List contains (eg using Generics) - this means this method can return a List containing any type. In the main method, you call this method and attempt to set the returned results to a List defined as containing objects of type "MyData"...this present a problem because there is no guarantee the returned List contains objects of this type. Your code could run flawlessly, but Generics provide compile time checks such as this which can prevent runtime exceptions. You can either suppress the warning (not recommended), or somehow define the List type
Lesson: Generics (Updated) (The Java™ Tutorials > Learning the Java Language)