今天在编译Java程序时遇到如下问题：
No enclosing instance of type PrintListFromTailToHead is accessible. Must qualify the allocation with an enclosing instance
of type PrintListFromTailToHead (e.g. x.new A() where x is an instance of PrintListFromTailToHead).
源代码为：
public class PrintListFromTailToHead {
public static void main(String[] args) {
ListNode one = new ListNode(1);
ListNode two = new ListNode(2);
ListNode three = new ListNode(3);
one.next = two;
two.next = three;
ArrayList result = printListFromTailToHead(one);
System.out.println("结果是：" + result);
}
class ListNode {
public int val;
public ListNode next;
public ListNode() {
}
public ListNode(int val) {
this.val = val;
}
}
public static ArrayList printListFromTailToHead(ListNode listNode) {
Stack stack = new Stack();
while (listNode != null) {
stack.push(listNode.val);
listNode = listNode.next;
}
ArrayList arrayList = new ArrayList();
while (!stack.isEmpty()) {
arrayList.add(stack.pop());
}
return arrayList;
}
}
问题解释：
代码中，我的ListNode类是定义在PrintListFromTailToHead类中的内部类。ListNode内部类是动态的内部类，而我的main方法是static静态的。
就好比静态的方法不能调用动态的方法一样。
有两种解决办法：
第一种：
将内部类ListNode定义成静态static的类。
第二种：
将内部类ListNode在PrintListFromTailToHead类外边定义。
两种解决方法：
第一种：
public class PrintListFromTailToHead {
public static void main(String[] args) {
ListNode one = new ListNode(1);
ListNode two = new ListNode(2);
ListNode three = new ListNode(3);
one.next = two;
two.next = three;
ArrayList result = printListFromTailToHead(one);
System.out.println("结果是：" + result);
}
static class ListNode {
public int val;
public ListNode next;
public ListNode() {
}
public ListNode(int val) {
this.val = val;
}
}
第二种：
public class PrintListFromTailToHead {
public static void main(String[] args) {
ListNode one = new ListNode(1);
ListNode two = new ListNode(2);
ListNode three = new ListNode(3);
one.next = two;
two.next = three;
}
public static ArrayList printListFromTailToHead(ListNode listNode) {
Stack stack = new Stack();
while (listNode != null) {
stack.push(listNode.val);
listNode = listNode.next;
}
ArrayList arrayList = new ArrayList();
while (!stack.isEmpty()) {
arrayList.add(stack.pop());
}
return arrayList;
}
}
class ListNode {
public int val;
public ListNode next;
public ListNode() {
}
public ListNode(int val) {
this.val = val;
}
}
以上所述是小编给大家介绍的Java解决No enclosing instance of type PrintListFromTailToHead is accessible问题的两种方案，希望对大家有所帮助。
