【157天】尚学堂高琪Java300集视频精华笔记（126）

决断。。。

第126集：引用类型_自定义数据排序

使用Comparable

1. 实体类中实现了ComparaTo方法

package test126;import java.text.SimpleDateFormat;
import java.util.Date;public class NewsItem1 implements Comparable<NewsItem1> {private String title;private int hits;private Date pubTime;public void setTitle(String title){this.title = title;}public String getTitle(){return title;}public void setHits(int hits){this.hits = hits;}public int getHits(){return hits;}public void setPubtime(Date pubTime){this.pubTime = pubTime;}public Date getPubtime(){return pubTime;}public NewsItem1(){}public NewsItem1(String title,int hits,Date pubTime){this.title = title;this.hits = hits;this.pubTime = pubTime;}public int compareTo(NewsItem1 o){//点击量升序，时间降序int result;result = this.hits - o.hits; //先比较点击量if(result==0){result = this.pubTime.compareTo(pubTime);//再比较时间if(result==0){result = this.title.compareTo(title);//最后再比较标题字符串}}return -result;// Collection.sort按从小到大排序，而我想要从小到大排序的结果，所以加负号}public String toString(){StringBuilder sb = new StringBuilder();sb.append("标题：").append(this.title);sb.append(",时间：").append(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(this.pubTime));sb.append(",点击量").append(this.hits).append("\n");return sb.toString();}}

1. Collection.sort是升序

package test126;import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.List;public class MySort1 {public static void main(String[] args){List<NewsItem1> news = new ArrayList<NewsItem1>();news.add(new NewsItem1("哈哈哈哈",50,new Date()));news.add(new NewsItem1("呵呵呵呵",100,new Date(System.currentTimeMillis()-1000*60*60)));news.add(new NewsItem1("妹妹诶诶",0,new Date(System.currentTimeMillis()+1000*60*60)));System.out.println("排序前"+news);Collections.sort(news);System.out.println("排序后"+news);}
}

使用Comparator

1. 实体类很干净~功能很单一

package test126;import java.text.SimpleDateFormat;
import java.util.Date;public class NewsItem2 {private String title;private int hits;private Date pubTime;public void setTitle(String title){this.title = title;}public String getTitle(){return title;}public void setHits(int hits){this.hits = hits;}public int getHits(){return hits;}public void setPubTime(Date pubTime){this.pubTime = pubTime;}public Date getPubTime(){return pubTime;}public NewsItem2(){}public NewsItem2(String title,int hits,Date pubTime){this.title = title;this.hits = hits;this.pubTime = pubTime;}public String toString(){StringBuilder sb = new StringBuilder();sb.append("标题：").append(this.title);sb.append(",时间：").append(new SimpleDateFormat("yyyy-MM-dd HH:mm:ss").format(this.pubTime));sb.append(",点击量").append(this.hits).append("\n");return sb.toString();}}

package test126;import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.List;public class MySort2 {public static void main(String[] args){List<NewsItem2> news = new ArrayList<NewsItem2>();news.add(new NewsItem2("哈哈哈哈哈",50,new Date()));news.add(new NewsItem2("呵呵呵呵",100,new Date(System.currentTimeMillis()-1000*60*60)));news.add(new NewsItem2("妹妹诶",0,new Date(System.currentTimeMillis()+1000*60*60)));System.out.println("排序前"+news);Collections.sort(news,new B());System.out.println("排序后"+news);}
}

1. 采用A方案排序

package test126;import java.util.Comparator;public class A implements Comparator<NewsItem2> {public int compare(NewsItem2 o1,NewsItem2 o2){//点击量升序，时间降序int result;result = o1.getHits() - o2.getHits(); //先比较点击量if(result==0){result = o1.getPubTime().compareTo(o2.getPubTime());//再比较时间if(result==0){result = o1.getTitle().compareTo(o2.getTitle());//最后再比较标题字符串}}return -result;// Collection.sort按从小到大排序，而我想要从小到大排序的结果，所以加负号}
}

1. 采用B方案排序

package test126;import java.util.Comparator;public class B implements Comparator<NewsItem2> {public int compare(NewsItem2 o1,NewsItem2 o2){//字符串长度int result = o1.getTitle().length()-o2.getTitle().length();//再比较时间return -result;}
}