JAVA Comparator 接口排序用法
java的比较器有两类，分别是Comparable接口和Comparator接口。
在为对象数组进行排序时，比较器的作用非常明显，首先来讲解Comparable接口。
让需要进行排序的对象实现Comparable接口，重写其中的compareTo(T o)方法，在其中定义排序规则，那么就可以直接调用java.util.Arrays.sort()来排序对象数组，实例如下：
class Student implements Comparable{
private String name;
private int age;
private float score;
public Student(String name, int age, float score) {
this.name = name;
this.age = age;
this.score = score;
}
public String toString()
{
return name+"\t\t"+age+"\t\t"+score;
}
@Override
public int compareTo(Student o) {
// TODO Auto-generated method stub
if(this.score>o.score)//score是private的，为什么能够直接调用,这是因为在Student类内部
return -1;//由高到底排序
else if(this.scoreo.age)
return 1;//由底到高排序
else if(this.age 执行的结果是
sunliu 22 100.0
wangwu 20 99.0
zhangsan 20 90.0
lisi 22 90.0
但是在设计类的时候，可能没有考虑到让类实现Comparable接口，那么就需要用到另外的一个比较器接口Comparator。
从上面的实例我们可以发现，compareTo(T o)只有一个参数，而Comparator接口中必须要实现的compare(T o1,T o2)就有两个参数。
代码实例
package edu.sjtu.ist.comutil;
import java.util.Comparator;
class Student {
private String name;
private int age;
private float score;
public Student(String name, int age, float score) {
this.name = name;
this.age = age;
this.score = score;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public float getScore() {
return score;
}
public void setScore(float score) {
this.score = score;
}
public String toString()
{
return name+"\t\t"+age+"\t\t"+score;
}
}
class StudentComparator implements Comparator{
@Override
public int compare(Student o1, Student o2) {
// TODO Auto-generated method stub
if(o1.getScore()>o2.getScore())
return -1;
else if(o1.getScore()o2.getAge())
return 1;
else if(o1.getAge() 程序运行的结果和上面是一样的
Array.sort是对数组进行排序，假如我们不想使用数组，想使用Collection接口下的集合，如想使用List，那么需要稍微做些修改：
package comparatorTest;
/**
* 定义一个学生类
* 包括学号，姓名，数学成绩，语文成绩
* @author zhangnan
*
*/
public class Student{
private String Name;
private int ID;
private int scoreMath;
private int scoreChi;
public Student (String name,int ID,int score1,int score2){
this.Name=name;
this.ID=ID;
this.scoreMath=score1;
this.scoreChi=score2;
}
public String getName(){
return this.Name;
}
public void setName(String pname){
this.Name=pname;
}
public int getID(){
return this.ID;
}
public void setID(int pID){
this.ID=pID;
}
public int getMathScore(){
return scoreMath;
}
public void setMathScore(int score1){
this.scoreMath=score1;
}
public float getChiScore(){
return scoreChi;
}
public void setChiScore(int score2){
this.scoreChi=score2;
}
/**
* 返回学生信息
*/
public String toString(){
return Integer.toString(ID)+"\t\t"+Name+"\t\t"+Integer.toString(scoreMath)+"\t\t"+Integer.toString(scoreChi);
}
}
--------------------------------------------------------------------------------
package comparatorTest;
import java.util.Comparator;
public class ComparatorSort implements Comparator {
public int compare(Student s1, Student s2) {
// TODO Auto-generated method stub
if (s1.getID() > s2.getID()) {
return 1;
} else if (s1.getID() < s2.getID()) {
return -1;
} else {
if (s1.getMathScore() > s2.getMathScore())
return -1;
else if (s1.getMathScore() < s2.getMathScore())
return 1;
else
return 0;
}
}
}
--------------------------------------------------------------------------------
package comparatorTest;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Random;
public class test {
public static void main(String[] args) {
// TODO Auto-generated method stub
Random random=new Random();
ArrayList st=new ArrayList();
Student s1= new Student("zhangnan1",random.nextInt(10),random.nextInt(100),random.nextInt(100));
Student s2= new Student("zhangnan2",random.nextInt(10),random.nextInt(100),random.nextInt(100));
Student s3= new Student("zhangnan3",random.nextInt(10),random.nextInt(100),random.nextInt(100));
Student s4= new Student("zhangnan4",random.nextInt(10),random.nextInt(100),random.nextInt(100));
st.add(s1);
st.add(s2);
st.add(s3);
st.add(s4);
System.out.println("全部的学生：");
Collections.sort(st,new ComparatorSort());
for(Student s:st){
System.out.println(s);
}
}
}
全部的学生：
0 zhangnan3 67 78
0 zhangnan2 39 0
2 zhangnan1 57 96
3 zhangnan4 62 53
在这里我们没有使用对象数组，而是使用了Collection 接口下的ArrayList 集合，所以排序用的是 Collections.sort(st,new ComparatorSort())