DAY13：尚学堂高琪JAVA（124~126）

Date类型的排序：整体与上一节冒泡排序一致，只需注意时间类型的数据比较不能直接相互减，要用.compareTo方法
DateSort.java

package sort;
//124 Date排序
import java.util.Arrays;
import java.util.Date;
public class DateSort {
	public static void main(String[] args) {
		Date[] arr=new Date[3];
		arr[0]=new Date();  
		arr[1]=new Date(System.currentTimeMillis()-1000*60*60);
		arr[2]=new Date(System.currentTimeMillis()+1000*60*60);
		sort(arr);
		Utils.sort(arr);
	}
	@SuppressWarnings({ "rawtypes", "unchecked" })
	public static void sort(Date[] arr) {
		for (int j = 0; j < arr.length - 1; j++) {
			boolean sorted = true;
			for (int i = 0; i < arr.length - 1 - j; i++) {
				if (((Comparable)(arr[i])).compareTo( arr[i + 1] )>0 ) {
					Date temp = arr[i];
					arr[i] = arr[i + 1];
					arr[i + 1] = temp;
					sorted = false;
				}
			}
			if (sorted) {
				break;
			}
		}
		System.out.println(Arrays.toString(arr));
	}
}

自定义类型的排序
方法一：实体类实现java.lang.Comparable并重写compareTo方法
方法二：提供额外的业务排序类，让其实现java.lang.Comparator并重写compare方法
实例一：

package sort;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Collections;
import java.util.Date;
import java.util.List;
import org.omg.Messaging.SyncScopeHelper;
import sort.Utils;
//126 引用类型的排序
public class NewsItemApp {
	public static void main(String[] args) {
		List<NewsItem> news=new ArrayList<NewsItem>();
		news.add(new NewsItem("bbbbb",50,new Date(System.currentTimeMillis()-60*60*1000)));
		news.add(new NewsItem("aaaaa",100,new Date()));
		news.add(new NewsItem("ccccc",60,new Date(System.currentTimeMillis()-60*60*1000)));
		// TODO Auto-generated method stub
		System.out.println("排序前："+news);
		Collections.sort(news);
		System.out.println("排序后："+news);
	}
}

package sort;
//126 引用类型的排序
import java.text.SimpleDateFormat;
import java.util.Date;
public class NewsItem implements java.lang.Comparable<NewsItem>{
	private String title;
	private int hits;
	private Date publictime;
	public NewsItem() {
	}
	public NewsItem(String title, int hits, Date publictime) {
		super();
		this.title = title;
		this.hits = hits;
		this.publictime = publictime;
	}
	public String getTitle() {
		return title;
	}
	public void setTitle(String title) {
		this.title = title;
	}
	public int getHits() {
		return hits;
	}
	public void setHits(int hits) {
		this.hits = hits;
	}
	public Date getPublictime() {
		return publictime;
	}
	public void setPublictime(Date publictime) {
		this.publictime = publictime;
	}
//时间降序，点击量升序，标题降序
	@Override
	public int compareTo(NewsItem o) {
		int result=0;
		result=-this.publictime.compareTo(o.publictime);
		if (result==0) {
			result=this.hits-o.hits;
			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("\t时间：").append(new SimpleDateFormat("YYYY-MM-dd HH:MM:SS").format(this.publictime));
		sb.append("\t点击量：").append(this.hits).append("\n");
		return sb.toString();
	}
}

实例二：
GoodsApp.java

package sort;
import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
public class GoodsApp {
	public static void main(String[] args) {
		// TODO Auto-generated method stub
		List<Goods> list=new ArrayList<Goods>();
		list.add(new Goods("Aava入门",50,1000));
		list.add(new Goods("Dava进阶",60,900));
		list.add(new Goods("Cava实战",70,5000));
		System.out.println("排序前："+list);
		//Collections.sort(list,new GoodsPriceComp());
		Collections.sort(list,new GoodsNameComp());
		System.out.println("排序前："+list);
	}
}

Goods.java

package sort;
/*126 实体类
 * */
public class Goods {
	private String name;
	private double price;
	private int fav;
	public Goods(){}
	public Goods(String name, double price, int fav) {
		super();
		this.name = name;
		this.price = price;
		this.fav = fav;
	}
	public String getName() {
		return name;
	}
	public void setName(String name) {
		this.name = name;
	}
	public double getPrice() {
		return price;
	}
	public void setPrice(double price) {
		this.price = price;
	}
	public int getFav() {
		return fav;
	}
	public void setFav(int fav) {
		this.fav = fav;
	}
	public String toString(){
		return "商品名：   "+this.getName()+"价格：     "+this.getPrice() +"收藏量：    "+this.fav+"\n";
	}
}

额外的业务排序类:
GoodsPriceComp.java

package sort;
/*
 * 按照价格排序的业务类（降序）*/
public class GoodsPriceComp implements java.util.Comparator<Goods> {
	public static void main(String[] args) {
	}
	@Override
	public int compare(Goods o1, Goods o2) {
		return -o1.getPrice()-o2.getPrice()>0?1:(o1.getPrice()-o2.getPrice()==0?0:-1);
	}
}

GoodsNameComp.java

package sort;
public class GoodsNameComp implements java.util.Comparator<Goods>{
	public static void main(String[] args) {
	}
	@Override
	public int compare(Goods o1, Goods o2) {
		// TODO Auto-generated method stub
		int temp=o1.getName().compareTo(o2.getName());
		return temp>0?1:(temp==0?0:-1);
	}
}

推荐用第二种，优势：
1.解耦：与实体类分开
2.方便：应对多变的排序规则