【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;     } }