Java Activity

MainActivity.java

package com.example.pack.two;

// some imports
import com.example.package.one.MyClass;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_java);

        MyClass myClass = new MyClass();
        myClass.setListener(new MyClass.Listener() {
            @Override
            public void foo() {

            }
        });

    }

}