为什么无法排序哪？
public   static   void   main(String[]   args)   {
ArrayList <Point>   l=new   ArrayList <Point> ();
Point   p1=new   Point(64,91);
Point   p2=new   Point(78,163);
Point   p3=new   Point(270,135);
Point   p4=new   Point(390,180);
Point   p5=new   Point(390,120);
l.add(p5);
l.add(p4);
l.add(p3);
l.add(p1);
l.add(p2);

for(int   i=0;i <l.size();i++){
System.out.print(l.get(i).x);
System.out.print( "   ");
System.out.println(l.get(i).y);
}
System.out.println( "================= ");

Collections.sort(l,new   myComparator());

for(int   i=0;i <l.size();i++){
System.out.print(l.get(i).x);
System.out.print( "   ");
System.out.println(l.get(i).y);
}
}
======================================================
public   class   myComparator   implements   Comparator   {

public   int   compare(Point   a,Point   b)   {
int   x1=a.x;
int   x2=b.x;
int   y1=a.y;
int   y2=b.y;
if(x1 <x2)
return   -1;
else  
return   1;
}

public   int   compare(Object   arg0,   Object   arg1)   {
//   TODO   Auto-generated   method   stub
return   0;
}
}

------解决方案--------------------
public int compare(Object arg0, Object arg1)
public int compare(Point a,Point b)
重載會出問題的

------解决方案--------------------
晕，没看到上面的public int compare(Point a,Point b)　，你写成这样是无效的．

------解决方案--------------------
public class myComparator implements Comparator {

public int compare(Object o1,Object o2) {
Point a, b;
if(o1 instanceof Point){
a = (Point) o1;
} else {
return -1;
}
if(o2 instanceof Point){
b = (Point) o2;
} else {
return -1;
}
int x1=a.x;
int x2=b.x;
int y1=a.y;
int y2=b.y;
if(x1 <x2)
return -1;
else
return 1;
}
}