class list {
    int value;
    list next;// =null;
}

public class linkList {

    list head = null;

    public void insert(int num) {
        list newNode = new list();
        list runner;
        list previouse;
        newNode.value = num;

        if (head == null) {
            head = newNode;
            newNode.next = null;
        } else {
            previouse = null;
            runner = head;

            while (runner != null && runner.value < num) { // 你的写法有点问题，应该先判断是否为null
                                                            // 在判断value，因为&&是短路操作符，如果runner为null了，就不会判断.value
                                                            // <  num,按照你的写法，如果runner为null则会报空指针
                previouse = runner;
                runner = runner.next;
            }
            if (previouse == null) {
                head = newNode;
                newNode.next = runner;
            } else if (runner == null) {
                previouse.next = newNode;
                newNode.next = runner;

            }

        }

    }

    public void printList() {
        list runner = new list();
        if (head == null)
            System.out.println("This is an empty list!");
        else {
            runner = head;
            while (runner != null) {
                System.out.println(runner.value);
                runner = runner.next;
            }
        }
    }

    public static void main(String[] args) {
        int number;
        linkList myList = new linkList();

         for (int i = 0; i < 10; i++) {
//        for (int i = 10; i > 0; i--) {
            myList.insert(i);
        }
        myList.printList();
    }

}