外部比較器,實現comparator,重寫compare,以下例子實現包含對象的集合的排序。排序時調用的函數是collections.sort(list,比較器)。
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.List;
/**
* @author :Handoking
* @date : 2019/5/24
*/
//外部比較器
class MyCompare implements Comparator<Students> {
@Override
public int compare(Students s1,Students s2){
if (s1.getAge()>s2.getAge()){
return 1;
}else if (s1.getAge()==s2.getAge()){
return 0;
}else{
return -1;
}
}
}
class Students{
private int age;
private String name;
public Students(int age, String name) {
this.age = age;
this.name = name;
}
public Students() {
}
public int getAge() {
return age;
}
public String getName() {
return name;
}
public void setAge(int age) {
this.age = age;
}
public void setName(String name) {
this.name = name;
}
@Override
public String toString(){
return "Name:"+name+",Age:"+age;
}
}
public class TestCompare{
public static void main(String[] args){
List<Students> arr = new ArrayList<>();
arr.add(new Students(20,"mark"));
arr.add(new Students(22,"kaven"));
arr.add(new Students(16,"daxia"));
arr.add(new Students(25,"handoking"));
Collections.sort(arr,new MyCompare());
System.out.println(arr.get(1).toStirng);
}
}
內部比較器就是把比較器定義在內部,這是要實現的接口爲comparable,重寫compareTo,實現包含實體類對象的集合的排序時,調用的是collections.sort(list).
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
/**
* @author :Handoking
* @date : 2019/5/24
*/
//內部比較器
class Students implements Comparable<Students> {
private int age;
private String name;
public Students(int age, String name) {
this.age = age;
this.name = name;
}
public Students() {
}
public int getAge() {
return age;
}
public String getName() {
return name;
}
public void setAge(int age) {
this.age = age;
}
public void setName(String name) {
this.name = name;
}
@Override
public int compareTo(Students s1){
if (this.getAge()>s1.getAge()){
return 1;
}else if (this.getAge()==s1.getAge()){
return 0;
}else{
return -1;
}
}
@Override
public String toString(){
return "Name:" + name +",Age:"+age;
}
}
public class TestCompare{
public static void main(String[] args){
List<Students> arr = new ArrayList<>();
arr.add(new Students(20,"mark"));
arr.add(new Students(22,"kaven"));
arr.add(new Students(16,"daxia"));
arr.add(new Students(25,"handoking"));
Collections.sort(arr);
System.out.println(arr.get(0).toString());
}
}