第一种写法为啥报异常

public class Test12 {
    
    
    public static void main(String[] args) {
    
    
        LinkedList<String> list = new LinkedList<>();
        list.add("tutu");
        list.add("小美");
        list.add("uphappy");
        System.out.println("list = " + list);
        list.add(1,"head");
        System.out.println("list = " + list);
        list.set(0,"dad");
        System.out.println("list = " + list);

        System.out.println(list.getFirst());
        System.out.println(list.getLast());

       //第一种
        boolean b = list.isEmpty();
        while (!b){
    
    
            System.out.print(list.pop()+" ");
        }
        //dad head 小美 uphappy Exception in thread "main" java.util.NoSuchElementException
        //	at java.util.LinkedList.removeFirst(LinkedList.java:270)
        //	at java.util.LinkedList.pop(LinkedList.java:801)
        //	at com.web.Test12.main(Test12.java:23)
       //第二种
        while(!list.isEmpty()){
    
    
            System.out.print(list.pop()+" ");
        }
        //dad head 小美 uphappy
    }
}