我正在 java.util.LinkedList 上使用 java.util.ListIterator,期望它像以下伪代码一样工作:
list = (1,2,3,4)
iterator.next should be 1
iterator.next should be 2
iterator.prev should be 1
iterator.next should be 2
但顺序是这样的:
iterator.next is 1
iterator.next is 2
iterator.prev is 2
iterator.next is 2
我不敢相信这就是它的工作方式,所以我创建了一个测试,但它产生了相同的输出。
所以我仔细研究了 ListIterator 的定义,当然是:
next()
Returns the next element in the list and advances the cursor position.
previous()
Returns the previous element in the list and moves the cursor position backwards.
所以实施是正确的,但我仍然有一个问题,为什么他们选择这种行为?我得到它的方式不是更直观吗?
这是测试的代码:
import static org.junit.Assert.assertEquals;
import org.junit.Before;
import org.junit.Test;
import java.util.LinkedList;
import java.util.ListIterator;
public class LinkedListTest {
ListIterator<Integer> iterator;
@Before
public void setUp() throws Exception {
LinkedList<Integer> list = new LinkedList<>();
for (int i = 1; i < 5; i++) {
list.add(i);
}
iterator = list.listIterator();
}
@Test
public void successfullTest() throws Exception
{
assertEquals(1, (int) iterator.next());
assertEquals(2, (int) iterator.next());
assertEquals(2, (int) iterator.previous());
assertEquals(2, (int) iterator.next());
assertEquals(3, (int) iterator.next());
assertEquals(4, (int) iterator.next());
}
@Test
public void failingTest() throws Exception
{
assertEquals(1, (int) iterator.next());
assertEquals(2, (int) iterator.next());
assertEquals(1, (int) iterator.previous());
assertEquals(2, (int) iterator.next());
assertEquals(3, (int) iterator.next());
assertEquals(4, (int) iterator.next());
}
}