TreeSet的两种排序方法：自然排序和定义比较器，推荐使用定义比较器方法。
- <span style="color:#333333;">import java.util.*;
- class treeset
- {
- public static void main(String[] args)
- {
- TreeSet t = new TreeSet();
- // TreeSet t = new TreeSet(new mycomparator());//第二种方法定义
- t.add(new student("a1",18));
- t.add(new student("a2",18));
- t.add(new student("a1",18));
- t.add(new student("a3",16));
- t.add(new student("a4",25));
- for(Iterator it = t.iterator();it.hasNext();)
- {
- student s = (student)it.next();
- sop(s.getName()+","+s.getAge());
- }
- }
- public static void sop(Object obj)
- {
- System.out.println(obj);
- }
- }
- /*
- 自然排序法 定义Comparable接口，覆盖CompareTo方法
- */
- class student implements Comparable
- {
- 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");
- 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;
- }
- }
- /*
- 定义比较器 当两种方法都存在时，以比较器为主。
- 定义一个类，实现Comparator接口，覆盖compare方法
- */
- class mycomparator implements Comparator
- {
- public int compare(Object o1,Object o2)
- {
- student s1 = (student)o1;
- student s2 = (student)o2;
- int num = s1.getName().compareTo(s2.getName());
- if(num ==0)
- {
- if(s1.getAge()>s2.getAge())
- return 1;
- if(s1.getAge()==s2.getAge())
- return 0;
- return -1;
- }
- return num;
- }
- }</span>
转载：http://blog.csdn.net/chaoyu168/article/details/49339771
