自定义类用比较器(Comparator)出错,怎么回事?
import java.util.*;class TreeSetTest
{
public static void main(String[] args)
{
//方法1 运用比较器
TreeSet<Object> ts=new TreeSet<Object>(new Student.StudentComparator());
//方法2 (由于实现了Comparable接口中的compareTo()方法,直接正常定义TreeSet的对象即可)
//TreeSet<Object> ts=new TreeSet<Object>();
ts.add(new Student(1,"lisi"));
ts.add(new Student(2,"wangwu"));
ts.add(new Student(3,"zhangsan"));
ts.add(new Student(3,"mybole"));
Iterator it=ts.iterator();
while(it.hasNext())
{
System.out.println(it.next());
}
}
}
class Student implements Comparable
{
int num;
String name;
static class StudentComparator implements Comparator//定义一个内部类实现Comparator接口
{
public int compare(Object o1,Object o2)
{
Student s1=(Student)o1;
Student s2=(Student)o2;
int result=s1.num>s2.num?1:(s1.num==s2.num?0:-1);
if(result==0)
{
result=s1.name.compareTo(s2.name);
}
return result;
}
}
Student(int num,String name)
{
this.num=num;
this.name=name;
}
public String toString()
{
return "num="+num+","+"name="+name;
}
public int compareTo(Object o)
{
Student s=(Student)o;
//return num>s.num?1:(num==s.num?0:-1);
int result=num>s.num?1:(num==s.num?0:-1);
if (result==0)
{
result= name.compareTo(s.name);
}
return result;
}
}
用方法2没问题,程序运行正确。
但用方法1时,编译的时候出错:使用了未经检查或不安全的操作。
改成了TreeSet<Object> ts=new TreeSet<Object>(new Student.StudentComparator<Object>());时
编译还是出错:Student.StudentComparator不带有参数。
额...头都晕了,我觉得是编译器版本的问题,怎么改才行啊,请大家指点下,谢谢了!!
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这么多天了,怎么都没人回答啊,着急哦!!
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