import java.util.ArrayList;
import java.util.List;

// As an example of a generic method, `slicesIndex` takes
// a list of any type T and an element of that type and returns
// the index of the first occurrence of v in s, or -1 if not present.
// Note that this method exists in the standard library
// as List.indexOf().
public static <T> int slicesIndex(List<T> s, T v) {
    for (int i = 0; i < s.size(); i++) {
        if (v.equals(s.get(i))) {
            return i;
        }
    }
    return -1;
}

// As an example of a generic class, `LinkedList` is a
// singly-linked list with values of any type.
public static class LinkedList<T> {
    private Node<T> head, tail;

    private static class Node<T> {
        T val;
        Node<T> next;

        Node(T val) {
            this.val = val;
        }
    }

    // We can define methods on generic classes just like we
    // do on regular classes.
    public void push(T v) {
        Node<T> newNode = new Node<>(v);
        if (tail == null) {
            head = tail = newNode;
        } else {
            tail.next = newNode;
            tail = newNode;
        }
    }

    // AllElements returns all the LinkedList elements as a list.
    public List<T> allElements() {
        List<T> elems = new ArrayList<>();
        for (Node<T> e = head; e != null; e = e.next) {
            elems.add(e.val);
        }
        return elems;
    }
}

public class Generics {
    public static void main(String[] args) {
        List<String> s = List.of("foo", "bar", "zoo");

        // When invoking generic methods, we can often rely
        // on type inference. Note that we don't have to
        // specify the type for T when calling slicesIndex
        // - the compiler infers it automatically.
        System.out.println("index of zoo: " + slicesIndex(s, "zoo"));

        // ... though we could also specify it explicitly.
        slicesIndex(s, "zoo");

        LinkedList<Integer> lst = new LinkedList<>();
        lst.push(10);
        lst.push(13);
        lst.push(23);
        System.out.println("list: " + lst.allElements());
    }
}