java 单链表

public class linked {

    private Note first;

    public void add(T t) {
        if (first == null) {
            first = new Note<>(t);
            return;
        }
        Note note = first;
        while (note != null) {
            if (note.next == null) {
                note.next = new Note<>(t);
                return;
            } else {
                note = note.next;
            }
        }
    }

    public Note getHead() {
        return first;
    }

    public T getT(Note note) {
        return note.t;
    }

    
    public void reversal() {
        //没数据或者只有一个数据的直接返回
        if (first == null || first.next == null) return;
        Note preNote = null;
        Note curNote = first;
        Note tem;//记录下次循环的开头节点
        while (curNote != null) {
            tem = curNote.next;
            curNote.next = preNote;
            preNote = curNote;
            curNote = tem;
        }
        first = preNote;
    }

    
    public void reversal(Note head) {
        if (head == null) return;
        if (head.next == null) {
            first = head;
            return;//可以返回最后节点，变成链表新的头节点
        }

        Note next = head.next;
        reversal(next);
        next.next = head;
        head.next = null;
    }

    public void printf() {
        Note note = this.first;
        while (note != null) {
            System.out.println(note.getT().toString());
            note = note.next;
        }
    }

    private static class Note {

        private E t;
        private Note next;

        public E getT() {
            return t;
        }

        public Note(E t) {
            this.t = t;
        }

        public Note getNext() {
            return next;
        }

    }

}