Question

java中两个list集合如何排序

有两个集合
List<Article> list1 = new ArrayList<Article>();
List<Article> list2 = new ArrayList<Article>();

里面有几个属性 ，Article.java如下：
private String title;
private String content;
private Date gxrq; ---->(java.util.Date类型)
现在需要根据 gxrq 进行排序
list1 是从一个表AT1中取出的数据，list2是从另外一个表AT2中取出的数据
请问怎样将这两个集合合成一个集合并且根据 gxrq 进行排序

请各位大侠门帮我写一下排序这个方法，谢谢了。

Answer 1

首先让你的Article实现Comparable这个接口..

然后根据他的gxrq进行比较..

集合合成的话
list1.addAll(list2)就行了。

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Date;
import java.util.List;

public class Article implements Comparable<Article> {

public static void main(String[] args) {
List<Article> list1 = new ArrayList<Article>();
List<Article> list2 = new ArrayList<Article>();
Article a1 = new Article();
a1.setGxrq(new Date(100, 5, 5));
Article a2 = new Article();
a2.setGxrq(new Date(100, 3, 5));
list1.add(a1);
list2.add(a2);
list1.addAll(list2);
Collections.sort(list1);
for(Article a : list1) {
System.out.println(a.getGxrq());
}
}

private String title;

private String content;

private Date gxrq;

public int compareTo(Article arg0) {
return this.gxrq.compareTo(arg0.gxrq);
}

public String getContent() {
return content;
}

public void setContent(String content) {
this.content = content;
}

public Date getGxrq() {
return gxrq;
}

public void setGxrq(Date gxrq) {
this.gxrq = gxrq;
}

public String getTitle() {
return title;
}

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

Answer 2

最正统的做法是自定义一个比较器，如下所示

public class ArticleComparator implements Comparator {

public int compare(Object o1, Object o2) {
Article c1 = (Article) o1;
Article c2 = (Article) o2;
if (c1.getGxrq().getTime() > c2.getGxrq().getTime()) {
return 1;
}
return -1;
}
}

主代码这样既可

List<Article> list1 = new ArrayList<Article>();
/*.....添加数据.......*/
List<Article> list2 = new ArrayList<Article>();
/*.....添加数据.......*/
list1.addAll(list2);
ArticleComparator articleComparator = new ArticleComparator();
Collections.sort(list1, articleComparator);

Answer 3

将两个list合并
List<Article> list1 = new ArrayList<Article>();
List<Article> list2 = new ArrayList<Article>();
list1.addAll(list2);
Collections.sort(list,new ReverseSort());
//自定义反向排序比较器
class ReverseSort implements Comparator{
public int compare(Object obj1,Object obj2) {
Article user1 = (Article)obj1;
Article user2 = (Article)obj2;
return -user1.gxrq.compareTo(user2.gxrq);
}
}

Answer 4

放到一个list中排序就可以了
List<Article> list = new ArrayList<Article>();
list.addAll(list1);
list.addAll(list2);
然后2层循环就可以了

Answer 5

List<String> list = new ArrayList<String>();
list.add("6");
list.add("5");
list.add("");
list.add("3");
list.add("1");
list.add("2");
list.add("4");

Collections.sort(list);