package cn.set;

import java.util.HashSet;
import java.util.Set;

class Student{
 int id;
 public Student(int id) {
  this.id = id;
 }
 @Override
 public String toString() {
  return this.id+"";
 }
 @Override
 public int hashCode() {
  return this.id;
 }
 @Override
 public boolean equals(Object obj) {
  if (obj instanceof Student){
   Student stu = (Student) obj;
   if (stu.id == this.id)
    return true;
  }
  return false;
 }
}
public class HashSetTest {
 public static void main(String[] args) {
  Set<Student> set = new HashSet<Student>();
  Student s1 = new Student(1);
  Student s2 = new Student(1);
  Student s3 = new Student(2);
  set.add(s1);
  set.add(s2);
  set.add(s3);
  for (Student s : set) {
   System.out.println(s);
  }
 }
}

package cn.set;

import java.util.Set;
import java.util.TreeSet;

class Student1 implements Comparable<Student1>{
 int id;
 public Student1(int id) {
  this.id = id;
 }
 @Override
 public String toString() {
  return this.id+"";
 }
 @Override
 public int hashCode() {
  return this.id;
 }
 @Override
 public boolean equals(Object obj) {
  if (obj instanceof Student1){
   Student1 stu = (Student1) obj;
   if (stu.id == this.id)
    return true;
  }
  return false;
 }
 public int compareTo(Student1 o) {
  return (this.id-o.id);
 }
}

public class TreeSetTest {
 public static void main(String[] args) {
  Set<Student1> set = new TreeSet<Student1>();
  Student1 s1 = new Student1(5);
  Student1 s2 = new Student1(1);
  Student1 s3 = new Student1(2);
  Student1 s4 = new Student1(4);
  Student1 s5 = new Student1(3);
  set.add(s1);
  set.add(s2);
  set.add(s3);
  set.add(s4);
  set.add(s5);
  for (Student1 s : set) {
   System.out.println(s);
  }
 }

}

package com.set;

import java.util.Set;
import java.util.TreeSet;

class Student1 implements Comparable<Student1>{
 int id;
 public Student1(int id) {
  this.id = id;
 }
 @Override
 public String toString() {
  return this.id+"";
 }
 @Override
 public int hashCode() {
  return this.id;
 }
 @Override
 public boolean equals(Object obj) {
  if (obj instanceof Student1){
   Student1 stu = (Student1) obj;
   if (stu.id == this.id)
    return true;
  }
  return false;
 }
 public int compareTo(Student1 o) {
  return (this.id-o.id);
 }
}

public class TreeSetTest {
 public static void main(String[] args) {
  Set<Student1> set = new TreeSet<Student1>();
  Student1 s1 = new Student1(5);
  Student1 s2 = new Student1(1);
  Student1 s3 = new Student1(2);
  Student1 s4 = new Student1(4);
  Student1 s5 = new Student1(3);
  set.add(s1);
  set.add(s2);
  set.add(s3);
  set.add(s4);
  set.add(s5);
  for (Student1 s : set) {
   System.out.println(s);
  }
 }

}

package cn.set;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;

class MySort1 implements java.util.Comparator<Student3>{
 public int compare(Student3 o1, Student3 o2) {
  return o2.id-o1.id;
 }
}
class Student3 implements Comparable<Student3>{
 int id;
 public Student3(int id) {
  this.id = id;
 }
 @Override
 public String toString() {
  return this.id+"";
 }
 public int compareTo(Student3 o) {
  return (this.id-o.id);
 }
}

public class ListSort {
 public static void main(String[] args) {
  List<Student3> list = new ArrayList<Student3>();
  Student3 s1 = new Student3(5);
  Student3 s2 = new Student3(1);
  Student3 s3 = new Student3(2);
  Student3 s4 = new Student3(4);
  Student3 s5 = new Student3(3);
  list.add(s1);
  list.add(s2);
  list.add(s3);
  list.add(s4);
  list.add(s5);
  System.out.println(list);
  //自然排序：
  Collections.sort(list);
  System.out.println(list);
  //客户排序
  Collections.sort(list, new MySort1());
  System.out.println(list);
 }
}