Strange Java syntax (for me at least)--怪异的Java语法

List<String> interests = new ArrayList<String>() {
            @Override
            public void add(int index, String element) {
                // TODO Auto-generated method stub
                super.add(index, element);
            }
        };

List<String> interests = new ArrayList<String>() {
        
            // Anonymous initialization block (vs static init block)
            {
                add("Java");
                add("C#");
            }
        };

public class MyClass {

    {
        doSomeThing();
        doSomeThing();
    }

    void doSomeThing() {
        System.out.println("doing");
    }

    public static void main(String[] args) {
        MyClass c = new MyClass();
    }
}

doing
doing