TreeSet的两种排序方法

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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>

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