我从头开始为链接列表类编写remove()方法时遇到一些问题。
有两个remove()方法，一个用于简单地删除链表的前面，另一个用于删除链表的特定索引处的数据。
我不确定哪一个被破坏了，我想我已经两个都正确但是通过运行我的另一个测试文件LinkedListTest，我收到有关remove()方法的错误消息：
Running Test remove tests (6 tests)
Starting tests: ....EE
Time: 0.004
There were 2 failures:
1) t44RemoveFromThreeItemList1(LinkedListTest$RemoveTest)
java.lang.AssertionError: Wrong item removed from One ItemList expected:<y> but was:<x>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
... 11 more
2) t45RemoveFromThreeItemList2(LinkedListTest$RemoveTest)
java.lang.AssertionError: Wrong item removed from One ItemList expected:<z> but was:<y>
at org.junit.Assert.fail(Assert.java:88)
at org.junit.Assert.failNotEquals(Assert.java:743)
at org.junit.Assert.assertEquals(Assert.java:118)
... 11 more
Test Failed! (2 of 6 tests failed.)
Test failures: abandoning other phases.
任何建议都表示赞赏，我已经看了很长时间，需要一些新鲜的眼睛。这是我的代码：
import java.util.*;
public class LinkedList<E> {
private class ListNode {
E data;
ListNode next;
ListNode(E data) {
this.data = data;
next = null;
}
ListNode(E data, ListNode next) {
this.data = data;
this.next = next;
}
}
private ListNode front;
private int size;
public LinkedList() {
front = null;
}
public int size() {
return size;
}
public boolean isEmpty() {
if (this.size == 0) {
return true;
} else {
return false;
}
}
public void add(E value) {
this.size++;
if (front == null) {
front = new ListNode(value);
} else {
ListNode current = front;
while (current.next != null) {
current = current.next;
}
current.next = new ListNode(value);
}
}
public void add(int index, E value) {
if (index == 0){
front = new ListNode(value, front);
}
else {
ListNode curr = front;
for (int i = 0; i < index - 1; i++){
curr = curr.next;
}
curr.next = new ListNode(value, curr.next);
}
}
public E get(int index) {
ListNode current = front;
for (int i = 0; i < this.size(); i++, current = current.next) {
if (i == index) {
return current.data;
}
}
return current.data;
}
public E remove() {
ListNode result = front;
front = front.next;
size--;
return result.data;
}
public E remove(int index) {
ListNode result;
if (index < 0 || index >= this.size()) {
throw new IndexOutOfBoundsException();
}
if (index == 0){
result = front;
front = front.next;
size--;
return result.data;
} else {
ListNode curr = front;
for (int i = 1; i < index; i++){
curr = curr.next;
}
result = curr;
curr.next = curr.next.next;
}
size--;
return result.data;
}
此外，这里是测试文件的相关部分，用于上下文：
public static class RemoveTest {
// Maximum 10 milliseconds for all tests
@Rule public Timeout timeout = new Timeout(10);
LinkedList<Character> oneList = null;
LinkedList<Character> threeList = null;
@Before public void setUp() {
oneList = new LinkedList<Character>();
oneList.add('a');
threeList = new LinkedList<Character>();
threeList.add('x');
threeList.add('y');
threeList.add('z');
}
@Test public void t41RemoveFromOneItemList() {
assertEquals("Wrong item removed from One ItemList",
new Character('a'), oneList.remove());
assertEquals("zero element list is not empty.",
true, oneList.isEmpty());
assertEquals("zero element list has wrong size.",
0, oneList.size());
}
@Test public void t42RemoveFromOneItemList() {
assertEquals("Wrong item removed from One ItemList",
new Character('a'), oneList.remove(0));
assertEquals("zero element list is not empty.",
true, oneList.isEmpty());
assertEquals("zero element list has wrong size.",
0, oneList.size());
}
@Test public void t42RemoveFromThreeItemList() {
assertEquals("Wrong item removed from One ItemList",
new Character('x'), threeList.remove());
assertEquals("two element list is empty.",
false, threeList.isEmpty());
assertEquals("two element list has wrong size.",
2, threeList.size());
assertEquals("get(0) on two element list is wrong.",
new Character('y'), threeList.get(0));
}
@Test public void t43RemoveFromThreeItemList0() {
assertEquals("Wrong item removed from One ItemList",
new Character('x'), threeList.remove(0));
assertEquals("two element list is empty.",
false, threeList.isEmpty());
assertEquals("two element list has wrong size.",
2, threeList.size());
assertEquals("get(0) on two element list is wrong.",
new Character('y'), threeList.get(0));
}
@Test public void t44RemoveFromThreeItemList1() {
assertEquals("Wrong item removed from One ItemList",
new Character('y'), threeList.remove(1));
assertEquals("two element list is empty.",
false, threeList.isEmpty());
assertEquals("two element list has wrong size.",
2, threeList.size());
assertEquals("get(0) on two element list is wrong.",
new Character('x'), threeList.get(0));
assertEquals("get(1) on two element list is wrong.",
new Character('z'), threeList.get(1));
}
@Test public void t45RemoveFromThreeItemList2() {
assertEquals("Wrong item removed from One ItemList",
new Character('z'), threeList.remove(2));
assertEquals("two element list is empty.",
false, threeList.isEmpty());
assertEquals("two element list has wrong size.",
2, threeList.size());
assertEquals("get(1) on two element list is wrong.",
new Character('y'), threeList.get(1));
}
}
答案 0 :(得分：0)
您的remove(index)方法出错。在循环中，如果要使用index = 1开始迭代，则必须使用curr初始化front.next，否则您将错过一个步骤。恕我直言，这样做更好：
public E remove(int index) {
ListNode result;
if (index < 0 || index >= this.size()) {
throw new IndexOutOfBoundsException();
}
ListNode curr = front;
for (int i = 0; i < index; i++){
curr = curr.next;
}
// front case added
if(index == 0){
front = curr.next;
}
result = curr;
curr.next = curr.next.next;
size--;
return result.data;
}