一、Comparator
强行对某个对象collection进行整体排序的比较函数，可以将Comparator传递给Collections.sort或Arrays.sort。接口方法：
public class SalesItemComparatorByFirstLetter implements Comparator<SalesItem> {
@Override
public int compare(SalesItem lhs, SalesItem rhs) {
return lhs.getFirstLetter().compareTo(rhs.getFirstLetter());
}
}SalesItem类里面存储有字母，这里根据字母来进行排序@Override
public int compareTo(Person o) {
return this.age.compareTo(o.getAge());
}
原文地址：http://blog.csdn.net/fanxl10/article/details/41745731
