什么是内部类，匿名内部类，静态内部类，外部类.?

一段代码做个总结.

class OutSideClass{
    //这是外部类
}

public class MainActivity extends AppCompatActivity {

    private class InnerClass{
        //这是内部类
    }

    private static class InnerStaticClass{
        //这是静态内部类
    }

    private interface AnonymityImpl{
        void func();
    }

    private abstract class AnonymityAbs{
        abstract void func();
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        AnonymityImpl functionImpl = new AnonymityImpl(){
            @Override
            public void func() {
                //这是匿名内部类
            }
        };
        AnonymityAbs anonymityAbs = new AnonymityAbs() {
            @Override
            void func() {
                //这是匿名内部类
            }
        };
    }
}