对其中某元素进行排序

import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;

public class test {

/**
* @param args
* @return
*/

public static void main(String[] args) {

TuanInfo tuan1 = new TuanInfo();
tuan1.setAaa(2);
tuan1.setBuyer(2);
TuanInfo tuan2 = new TuanInfo();
tuan2.setAaa(1);
tuan2.setBuyer(1);
TuanInfo tuan3 = new TuanInfo();
tuan3.setAaa(3);
tuan3.setBuyer(3);
List<TuanInfo> list = new ArrayList<TuanInfo>();
list.add(tuan3);
list.add(tuan2);
list.add(tuan1);
for (TuanInfo t : list) {
System.out.println(t.getBuyer() + " " + t.getAaa());
}
Collections.sort(list, new BuyerCompare());
for (TuanInfo t : list) {
System.out.println(t.getBuyer() + " " + t.getAaa());
}

}
}

class TuanInfo {
int buyer;
int aaa;

public int getBuyer() {
return buyer;
}

public void setBuyer(int buyer) {
this.buyer = buyer;
}

public int getAaa() {
return aaa;
}

public void setAaa(int aaa) {
this.aaa = aaa;
}

}

class BuyerCompare implements Comparator<TuanInfo> {
public int compare(TuanInfo o1, TuanInfo o2) {
if (o1.getBuyer() > o2.getBuyer())
return -1;
else
return 1;
}
}