Java 排序 Compare
在Java中使用集合来存储数据时非常常见的,集合排序功能也是常用功能之一.下面看一下如何进行集合排序,常用的方法有: Comparator和Comparable
Comparator接口
使用步骤:
- 新建比较类,
- 实现Comparator接口,
- 重写compare方法,
- package sort;
- import java.util.Comparator;
- public class LuckBoyCompare implements Comparator<LuckBoy>{
- @Override
- public int compare(LuckBoy o1, LuckBoy o2) {
- return o1.getAge()-o2.getAge();
- }
- }
- 调用
Collections.sort()方法进行排序, - 形式:
Collections.sort(集合, 比较器实例).
- @Test
- public void test1() {
- List<LuckBoy> boyList = new ArrayList<LuckBoy>();
- LuckBoy boy1 = new LuckBoy("张三",13,"上海");
- LuckBoy boy2 = new LuckBoy("李四",12,"北京");
- LuckBoy boy3 = new LuckBoy("王五",18,"深圳");
- LuckBoy boy4 = new LuckBoy("马六",17,"南京");
- boyList.add(boy1);
- boyList.add(boy2);
- boyList.add(boy3);
- boyList.add(boy4);
- System.out.println("排序前:");
- for (LuckBoy luckBoy : boyList) {
- System.out.println(luckBoy);
- }
- System.out.println("排序后:");
- Collections.sort(boyList, new LuckBoyCompare());
- for (LuckBoy luckBoy : boyList) {
- System.out.println(luckBoy);
- }
- }
LuckBoy.java
- package sort;
- public class LuckBoy{
- private String name;
- private Integer age;
- private String city;
- public LuckBoy() {
- super();
- }
- public LuckBoy(String name, Integer age, String city) {
- super();
- this.name = name;
- this.age = age;
- this.city = city;
- }
- public String getName() {
- return name;
- }
- public void setName(String name) {
- this.name = name;
- }
- public Integer getAge() {
- return age;
- }
- public void setAge(Integer age) {
- this.age = age;
- }
- public String getCity() {
- return city;
- }
- public void setCity(String city) {
- this.city = city;
- }
- @Override
- public String toString() {
- return "LuckBoy [name=" + name + ", age=" + age + ", city=" + city + "]";
- }
- }
打印结果:
排序前:
LuckBoy [name=张三, age=13, city=上海]
LuckBoy [name=李四, age=12, city=北京]
LuckBoy [name=王五, age=18, city=深圳]
LuckBoy [name=马六, age=17, city=南京]
排序后:
LuckBoy [name=李四, age=12, city=北京]
LuckBoy [name=张三, age=13, city=上海]
LuckBoy [name=马六, age=17, city=南京]
LuckBoy [name=王五, age=18, city=深圳]
Comparable接口
使用步骤:
- 数据模型实现Comparable接口,
- 重写compareTo方法,
- package sort;
- public class LuckBoy implements Comparable<LuckBoy>{
- //TODO 中间代码省略
- @Override
- public int compareTo(LuckBoy o) {
- return this.age-o.age;
- }
- }
- 调用
Collections.sort()方法进行排序, - 形式:
Collections.sort(集合)
- @Test
- public void test2() {
- List<LuckBoy> boyList = new ArrayList<LuckBoy>();
- LuckBoy boy1 = new LuckBoy("张三",13,"上海");
- LuckBoy boy2 = new LuckBoy("李四",12,"北京");
- LuckBoy boy3 = new LuckBoy("王五",18,"深圳");
- LuckBoy boy4 = new LuckBoy("马六",17,"南京");
- boyList.add(boy1);
- boyList.add(boy2);
- boyList.add(boy3);
- boyList.add(boy4);
- System.out.println("============================");
- System.out.println("排序前:");
- for (LuckBoy luckBoy : boyList) {
- System.out.println(luckBoy);
- }
- System.out.println("排序后:");
- Collections.sort(boyList);
- for (LuckBoy luckBoy : boyList) {
- System.out.println(luckBoy);
- }
- }
打印结果:
排序前:
LuckBoy [name=张三, age=13, city=上海]
LuckBoy [name=李四, age=12, city=北京]
LuckBoy [name=王五, age=18, city=深圳]
LuckBoy [name=马六, age=17, city=南京]
排序后:
LuckBoy [name=李四, age=12, city=北京]
LuckBoy [name=张三, age=13, city=上海]
LuckBoy [name=马六, age=17, city=南京]
LuckBoy [name=王五, age=18, city=深圳]
区别
Comparator 使用灵活,不需要修改源码.但是,使用时需要传入比较器对象;
Comparable 使用简单,但是需要修改源码.