List的正序和倒序排列

public class TestComparator {
public static void main(String[] args) {
List<Integer> listnum = new ArrayList<Integer>();
listnum.add(1);
listnum.add(2);
listnum.add(3);
listnum.add(4);
listnum.add(5);

System.out.println("升序排序测试:");
Comparator<Integer> ascComparator = new NumComparator();//NumComparator自定义的另外一个类，用来判断两数之间的大小

Collections.sort(listnum, ascComparator);
for (int i = 0; i < listnum.size(); i++) {
System.out.print(listnum.get(i) + " ");
}

System.out.println("\n降序排序测试:");
Comparator<Integer> descComparator = Collections.reverseOrder(ascComparator);
Collections.sort(listnum, descComparator);
for (int i = 0; i < listnum.size(); i++) {
System.out.print(listnum.get(i) + " ");
}
}
}
class NumComparator implements Comparator<Integer> {
public int compare(Integer o1, Integer o2) {
return o1 - o2;
}
}

结果：

升序排序测试:

1 2 3 4 5

降序排序测试:

5 4 3 2 1

注：转载原文http://blog.csdn.net/wminxue319/article/details/7382540