import java.util.*;
/*
当元素自身不具备比较性时，或者具备的比较性不是所需要的。
这时就需要让集合自身具备比较性。
定义了比较器，将比较器对象作为参数传递给TreeSet集合的构造函数。
当两种排序都存在时，以比较器为主。
定义一个类，实现Comparator接口，覆盖compare方法。
以return
*/
class Student implements Comparable//让学生具备比较性
{
private String name;
private int age;
Student(String name,int age)
{
this.name=name;
this.age=age;
}
public int compareTo(Object obj)
{
if(!(obj instanceof Student))
throw new RuntimeException("不是学生对象");
Student s = (Student) obj;
if(this.age>s.age)
return 1;
if(this.age==s.age)
return this.name.compareTo(s.name);
return -1;
}
public String getName()
{
return name;
}
public int getAge()
{
return age;
}
}
class TreeSetDemo2
{
public static void main(String[] args)
{
TreeSet ts = new TreeSet(new MyCompare());
ts.add(new Student("lisi02",20));
ts.add(new Student("lisi01",20));
ts.add(new Student("lisi05",25));
ts.add(new Student("lisi06",19));
//ts.add(new Student("lisi07",17));
Iterator it = ts.iterator();
while(it.hasNext())
{
Student stu = (Student)it.next();
System.out.println(stu.getName()+"....."+stu.getAge());
}
}
}
class MyCompare implements Comparator
{
public int compare (Object o1,Object o2)
{
//类型强转
Student s1 = (Student)o1;
Student s2 = (Student)o2;
int num=return s1.getName().compareTo(s2.getName());
if(num==0)
{
return new Integer(s1.getAge()).compareTo(new Integer(s2.getAge()));
}
}
} |
|
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