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<Integer> 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<Integer> printListFromTailToHead(ListNode listNode) { Stack<Integer> stack = new Stack<Integer>(); while (listNode != null) { stack.push(listNode.val); listNode = listNode.next; } ArrayList<Integer> arrayList = new ArrayList<Integer>(); 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<Integer> 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<Integer> printListFromTailToHead(ListNode listNode) { Stack<Integer> stack = new Stack<Integer>(); while (listNode != null) { stack.push(listNode.val); listNode = listNode.next; } ArrayList<Integer> arrayList = new ArrayList<Integer>(); 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。
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