集合操作--多条件排序

[java]代码库

1.Main
package s0223多条件排序;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Date;
import java.util.List;

public class Main {

	public static void main(String[] args) {
       List<NewsItem> news=new ArrayList<NewsItem>();
       news.add(new NewsItem("中国登上钓鱼岛",100,new Date(System.currentTimeMillis() ) ) );
       news.add(new NewsItem("中国GDP总量",40,new Date(System.currentTimeMillis() ) ) );
       news.add(new NewsItem("美国总统与xx会晤",60, new Date(System.currentTimeMillis() ) ) );
       
       System.out.println("排序前:"+news);
       Collections.sort(news);
       //因为news中的元素都是Comparable的实现类的实例,所以默认使用指定的Comparator
       //如果使用comparator的实现类,那么要指定comparator
       System.out.println("排序后:"+news);

	}

}

2.NewsItem类,在这个类中定义了排序优先级和排序顺序
package s0223多条件排序;
import java.text.SimpleDateFormat;
//新闻按时间降序,点击量升序,标题降序
import java.util.Date;

public class NewsItem implements java.lang.Comparable<NewsItem>{
    private String title;
    private int  hit;
    private Date pubTime;
    

    public NewsItem(){}


	public NewsItem(String title, int hit, Date pubTime) 
	{
		super();
		this.title = title;
		this.hit = hit;
		this.pubTime = pubTime;
	}
	
	//新闻按时间降序,点击量升序,标题降序,3个if嵌套,规定了排序的优先级
	public int compareTo(NewsItem o) 
	{
		int result=0;
		result=-this.pubTime.compareTo(o.pubTime);//加了- 变成降序
		if(result==0)
		{  
			result=this.hit-o.hit;
			if(result==0)
			{
				result=this.title.compareTo(o.title);
			}	
		}	
		return result;
	}
	
	public String toString()
	{
		StringBuilder sb=new StringBuilder();
		sb.append("  标题:").append(this.title);
		sb.append("  时间:").append(new SimpleDateFormat("yyyy-MM-dd").format(this.pubTime));
		sb.append("  点击量:").append(this.hit).append("\n");
		String str=sb.toString();
		return str;

	}


	public String getTitle() {
		return title;
	}

	public void setTitle(String title) {
		this.title = title;
	}

	public int getHit() {
		return hit;
	}

	public void setHit(int hit) {
		this.hit = hit;
	}

	public Date getPubTime() {
		return pubTime;
	}

	public void setPubTime(Date pubTime) {
		this.pubTime = pubTime;
	}
	
	
	
}