今年早些时候,我为我的java类编写了一个链表实现。这是一个名为LList的泛型类。我们现在必须为实验室编写合并排序算法。我决定重新使用之前创建的通用列表,而不是创建一个使用Ints的新列表实现。
The problem is how do I compare two generic objects? java wont let me do something like
if(first.headNode.data > second.headNode.data)
所以,我的问题是,它们是否是实现某种对任何类型的数据都有效的比较函数的一种方法?我尝试了以下操作:
String one, two;
one = first.headNode.data.toString();
two = second.headNode.data.toString();
if(first.headNode.data.compareTo(second.headNode.data) < 0) {
result.add(first.headNode.data);
// remove head node. remove() takes care of list size.
first.remove(1);
} else {
// If compareTo returns 0 or higher, second.headNode is lower or
// equal to first.headNode. So it s safe to update the result
// list
result.add(second.headNode.data);
second.remove(1);
}
这甚至不能正常工作。我用数字6和12进行了测试,上面的数字在结果列表中增加了12。
相关资料:
private LList<T> mergeSort(LList<T> list) {
LList<T> first = new LList();
LList<T> second = new LList();
if (list.length() == 1) {
return list;
}
int middle = list.length() / 2;
second.headNode = list.getNodeAt(middle + 1);
second.length = list.length() - (middle);
// Set first half to full list, then remove the "second" half.
first.headNode = list.headNode;
first.length = middle;
first.getNodeAt(middle).next = null;
// Get the splitted halves.
first = mergeSort(first);
second = mergeSort(second);
return merge(first, second);
}
private LList<T> merge(LList<T> first, LList<T> second) {
LList<T> result = new LList();
while((first.length > 0) && (second.length > 0)) {
// Ok, lets force toString to compare stuff since generics are a pain.
String one, two;
one = first.headNode.data.toString();
two = second.headNode.data.toString();
if(one.compareTo(two)) < 0) {
result.add(first.headNode.data);
// remove head node. remove() takes care of list size.
first.remove(1);
} else {
// If compareTo returns 0 or higher, second.headNode is lower or
// equal to first.headNode. So it s safe to update the result
// list
result.add(second.headNode.data);
second.remove(1);
}
}
return result;
}
NOTE: entire LList class can be found [here](http://rapidshare.com/files/219112739/LList.java.html MD5: BDA8217D0756CC171032FDBDE1539478)