java的工具类collections例子

import java.util.Collections;import java.util.Comparator;import java.util.Iterator;import java.util.LinkedList;import java.util.TreeSet;public class CollectionsTest{public static void main(String[] args){TreeSet set = new TreeSet(new PeopleComparator());LinkedList list = new LinkedList();set.add(new People(10));set.add(new People(20));set.add(new People(30));System.out.println("orginal order:");for(Iterator it = set.iterator(); it.hasNext();){People p = (People)it.next();System.out.println(p.age);list.add(p.age);}System.out.println("Maximum value ： " + Collections.max(list));System.out.println("Minimum value : " + Collections.min(list));System.out.println("reverse order:");Comparator c = Collections.reverseOrder();Collections.sort(list,c);for(Iterator it = list.iterator(); it.hasNext();){System.out.println(it.next());}System.out.println("random order:");Collections.shuffle(list);for(Iterator it = list.iterator(); it.hasNext();){System.out.println(it.next());}}}class People{int age;People(int age){this.age = age;}}class PeopleComparator implements Comparator{@Overridepublic int compare(Object o1, Object o2){People p1 = (People)o1;People p2 = (People)o2;return p1.age - p2.age;}}