TreeSet集合内部排序

import java.util.*; /* TreeSet集合内部实现了排序 1. 自定义对象需要实现Comparable接口的compareTo方法，自定义排序规则,return 1（第一个元素大于第二个元素），0（相等），-1（小于） 【正数负数均可，不一定要是1或者-1】 2. 如果元素本身的排序规则不适用，那么自定义比较器实现Comparator接口，并在初始化集合的时传入。 3. 底层数据结构是二叉树，大于放右边，小于放左边 */ class TreeSetDemo { public static void main(String[] args) { TreeSet ts = new TreeSet(new Mycompare()); // ts.add(new People("张三",3)); // ts.add(new People("赵一",9)); // ts.add(new People("李四",4)); // ts.add(new People("王五",5)); // ts.add(new People("李四四",4)); ts.add(new People("a02",3)); ts.add(new People("a01",5)); ts.add(new People("a39",9)); ts.add(new People("a40",7)); System.out.println(ts); Iterator i = ts.iterator(); while(i.hasNext()) { People p = (People) i.next(); System.out.println(p.getName() + "....." + p.getAge()); } } } // 元素类实现Comparable接口，复写compareTo方法 class People implements Comparable { private String name; private int age; People (String name, int age) { this.name = name; this.age = age; } public String getName() { return this.name; } public int getAge(){ return this.age; } public int compareTo (Object obj) { People p = (People) obj; if (this.age > p.age) { return 1; } else if (this.age == p.age){ return this.name.compareTo(p.name); } return -1; } } // 比较器实现Comparator接口，复写compare方法 class Mycompare implements Comparator { public int compare(Object o1, Object o2) { People p1 = (People) o1; People p2 = (People) o2; int num = p1.getName().compareTo(p2.getName()); if (num == 0) { return p1.getAge() - p2.getAge(); } return num; } }