你必须修改类ComplexComparator
就像下面这样,至少......
import java.util.Comparator;
public class ComplexComparator implements Comparator<Student> {
private Comparator<Student> comparatorOne;
private Comparator<Student> comparatorTwo;
public ComplexComparator(Comparator<Student> one,
Comparator<Student> another) {
this.comparatorOne = one;
this.comparatorTwo = another;
}
@Override
public int compare(Student one, Student another) {
// make a first comparison using comparator one
int comparisonByOne = comparatorOne.compare(one, another);
// check if it was 0 (items equal in that attribute)
if (comparisonByOne == 0) {
// if yes, return the result of the next comparison
return comparatorTwo.compare(one, another);
} else {
// otherwise return the result of the first comparison
return comparisonByOne;
}
}
}
对于两个以上Comparator
你将需要一个List
它们(或另一个重载的构造函数)和一个保持一定比较顺序的循环。
EDIT
对于您有关排序顺序的附加要求,这可能会有所帮助:
public class ComplexComparator implements Comparator<Student> {
private Comparator<Student> comparatorOne;
private Comparator<Student> comparatorTwo;
private boolean orderOneAscending = true;
private boolean orderTwoAscending = true;
/**
* Constructor without any sort orders
* @param one a comparator
* @param another another comparator
*/
public ComplexComparator(Comparator<Student> one, Comparator<Student> another) {
this.comparatorOne = one;
this.comparatorTwo = another;
}
/**
* Constructor that provides the possibility of setting sort orders
* @param one a comparator
* @param orderOneAscending sort order for comparator one
* (true = ascending, false = descending)
* @param another another comparator
* @param orderTwoAscending sort order for comparator two
* (true = ascending, false = descending)
*/
public ComplexComparator(Comparator<Student> one, boolean orderOneAscending,
Comparator<Student> another, boolean orderTwoAscending) {
this.comparatorOne = one;
this.comparatorTwo = another;
this.orderOneAscending = orderOneAscending;
this.orderTwoAscending = orderTwoAscending;
}
@Override
public int compare(Student one, Student another) {
int comparisonByOne;
int comparisonByAnother;
if (orderOneAscending) {
/* note that your lexicographical comparison in NameComparator
returns a negative integer if the String is greater!
If you take two numerical Comparators, the order will
turn into the opposite direction! */
comparisonByOne = comparatorOne.compare(another, one);
} else {
comparisonByOne = comparatorOne.compare(one, another);
}
if (orderTwoAscending) {
comparisonByAnother = comparatorTwo.compare(one, another);
} else {
comparisonByAnother = comparatorTwo.compare(another, one);
}
if (comparisonByOne == 0) {
return comparisonByAnother;
} else {
return comparisonByOne;
}
}
}
只需尝试一下这些值并尝试一些修改即可熟悉有关比较和排序的常见问题。
我希望这会有所帮助...