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.
