因此,我创建了一个名为"Sack“的通用数据结构。在这个过程中,我将物品添加到一个袋子中,抓取一个随机的物品,看看它是否是空的,或者倾倒它的内容物等等。我还创建了它来扩展以容纳所需的任意数量的物品。
移除帮助器方法应移除指定索引处的基础数据结构中的项。它应该通过将其替换为底层数组中的“最后一个”元素来实现。它还应该确保任何未使用的元素都是空的。
目前,我正在开发remove方法,但在remove方法上遇到了问题。当我运行我的测试时,我收到错误,说它没有正确的修饰符。因此我的代码是
public class Sack<E>
{
public static final int DEFAULT_CAPACITY = 10;
private E [] elementData;
private int size;
@SuppressWarnings("unchecked")
public Sack()
{
elementData = (E[]) new Object[DEFAULT_CAPACITY];
}
@SuppressWarnings("unchecked")
public Sack(int capacity)
{
if(capacity < 0)
{
throw new IllegalArgumentException("capacity " + capacity);
}
this.elementData = (E[]) new Object[capacity];
}
public boolean isEmpty()
{
if(size == 0)
{
return true;
}
else
{
return false;
}
}
public void add(E item)
{
int index = size++;
if(size >= elementData.length-1)
{
elementData = Arrays.copyOf(elementData, size);
}
elementData[index] = item;
}
public E [] dump()
{
E [] E2 = Arrays.copyOf(elementData, size);
for(int i = 0; i < size; i++)
{
elementData[i] = null;
}
size = 0;
return E2;
}
我在此处的删除中收到错误
public void remove(int index)
{
for (int i = index; i < size; i++)
{
elementData[i] = elementData[i + 1];
}
size--;
}
}
它期望接收的值是2,但是它接收的值是1。下拉任何方法来确保这一点。
下面是我的测试。我不能修改我的测试,只能修改我的代码。我在第一行收到一个错误。我将对其进行注释,以便您可以看到。
@Test
public void testRemove()
{
assertEquals(2, remove.getModifiers(), "remove does not have the correct modifiers"); // I receive an error here.
try
{
Random rand = new Random();
Integer[] setElementData = new Integer[10];
ArrayList<Integer> expectedElements = new ArrayList<Integer>();
int randElement;
for(int i=0; i<10; ++i)
{
randElement = rand.nextInt(50) + 1;
setElementData[i] = randElement;
expectedElements.add(randElement);
}
elementData.set(s, setElementData);
size.set(s, 10);
int randIndex;
int numEe;
while(!expectedElements.isEmpty()) {
numEe = expectedElements.size()-1;
randIndex = rand.nextInt(expectedElements.size());
expectedElements.set(randIndex, expectedElements.get(numEe));
expectedElements.remove(numEe);
remove.invoke(s, randIndex);
assertEquals(expectedElements.size(), size.get(s), "remove is not working correctly (check size usage)"); //Error now takes place here.
for(int i=0; i<expectedElements.size(); ++i) {
assertEquals(expectedElements.get(i), ((Object[])elementData.get(s))[i], "remove is not working correctly (sack array element order incorrect)");
}
assertNull(((Object[])elementData.get(s))[expectedElements.size()], "remove is not working correctly (sack array element not nullified correctly)");
}
assertEquals(0, size.get(s), "remove is not working correctly (check size usage)");
} catch (Exception e) {
fail("remove is not working correctly");
}
}
发布于 2019-03-06 01:26:01
我想通了。它最终通过了所有的测试,尽管这是非常困难的。代码如下:
private void remove( int index)
{
if(index >= 0)
{
E last = elementData[size - 1];
elementData[index] = last;
elementData[--size] = null;
}
}
发布于 2019-03-05 14:00:00
这将保持顺序:
public void remove(final int index) {
if (index >= size || 0 > index) {
// TODO better to throw 'new ArrayIndexOutOfBoundsException(index)'
// when remove illegal index
return;
}
if (index < size - 1) { // move whole array
System.arraycopy(
elementData, index + 1, // copy from
elementData, index, // copy to
size - index - 1); // copy length
}
elementData[--size] = null;
}
发布于 2019-03-04 05:30:48
尝试将其替换为:
public void remove(int index)
{
if(index >= 0) {
E last = elementData[size - 1];
elementData[index] = last;
size--;
}
}
https://stackoverflow.com/questions/54973786
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