我读过关于使用比较器排序数组列表的内容,但在所有的例子中,人们都使用了compareTo,根据一些研究,它是字符串的一种方法。

我想根据自定义对象的一个属性(Date对象)对其数组列表进行排序 (getStartDay())。通常我通过item1.getStartDate().before(item2.getStartDate())比较它们,所以我想知道我是否可以写一些像这样的东西:

public class CustomComparator {
    public boolean compare(Object object1, Object object2) {
        return object1.getStartDate().before(object2.getStartDate());
    }
}

public class RandomName {
    ...
    Collections.sort(Database.arrayList, new CustomComparator);
    ...
}

当前回答

我已经尝试了很多不同的解决方案,可在互联网上,但解决方案,为我是可在下面的链接。

https://www.java67.com/2017/07/how-to-sort-arraylist-of-objects-using.html

其他回答

我已经尝试了很多不同的解决方案,可在互联网上,但解决方案,为我是可在下面的链接。

https://www.java67.com/2017/07/how-to-sort-arraylist-of-objects-using.html

您可以使用Bean Comparator对自定义类中的任何属性进行排序。

import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Collections;
import java.util.Comparator;
import java.util.Date;

public class test {

public static class Person {
    public String name;
    public int id;
    public Date hireDate;

    public Person(String iname, int iid, Date ihireDate) {
        name = iname;
        id = iid;
        hireDate = ihireDate;
    }

    public String toString() {
        return name + " " + id + " " + hireDate.toString();
    }

    // Comparator
    public static class CompId implements Comparator<Person> {
        @Override
        public int compare(Person arg0, Person arg1) {
            return arg0.id - arg1.id;
        }
    }

    public static class CompDate implements Comparator<Person> {
        private int mod = 1;
        public CompDate(boolean desc) {
            if (desc) mod =-1;
        }
        @Override
        public int compare(Person arg0, Person arg1) {
            return mod*arg0.hireDate.compareTo(arg1.hireDate);
        }
    }
}

public static void main(String[] args) {
    // TODO Auto-generated method stub
    SimpleDateFormat df = new SimpleDateFormat("mm-dd-yyyy");
    ArrayList<Person> people;
    people = new ArrayList<Person>();
    try {
        people.add(new Person("Joe", 92422, df.parse("12-12-2010")));
        people.add(new Person("Joef", 24122, df.parse("1-12-2010")));
        people.add(new Person("Joee", 24922, df.parse("12-2-2010")));
    } catch (ParseException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    Collections.sort(people, new Person.CompId());
    System.out.println("BY ID");
    for (Person p : people) {
        System.out.println(p.toString());
    }

    Collections.sort(people, new Person.CompDate(false));
    System.out.println("BY Date asc");
    for (Person p : people) {
        System.out.println(p.toString());
    }
    Collections.sort(people, new Person.CompDate(true));
    System.out.println("BY Date desc");
    for (Person p : people) {
        System.out.println(p.toString());
    }

}

}

因为技术每天都在出现,所以答案会随着时间的推移而改变。我看了一下LambdaJ,看起来很有趣。

您可以尝试使用LambdaJ解决这些任务。你可以在这里找到它:http://code.google.com/p/lambdaj/

这里有一个例子:

这种迭代

List<Person> sortedByAgePersons = new ArrayList<Person>(persons);
Collections.sort(sortedByAgePersons, new Comparator<Person>() {
        public int compare(Person p1, Person p2) {
           return Integer.valueOf(p1.getAge()).compareTo(p2.getAge());
        }
});

用排序

List<Person> sortedByAgePersons = sort(persons, on(Person.class).getAge()); 

当然,拥有这种美感会影响性能(平均2次),但你能找到更可读的代码吗?

JAVA 8最简单的方法是英文字母排序

类的实现

public class NewspaperClass implements Comparable<NewspaperClass>{
   public String name;

   @Override
   public int compareTo(NewspaperClass another) {
      return name.compareTo(another.name);
   }
}

Sort

  Collections.sort(Your List);

如果你想为包含非英语字符的字母排序,你可以使用Locale…下面代码使用土耳其字符排序…

类的实现

public class NewspaperClass implements Comparator<NewspaperClass> {
   public String name;
   public Boolean isUserNewspaper=false;
   private Collator trCollator = Collator.getInstance(new Locale("tr_TR"));



   @Override
   public int compare(NewspaperClass lhs, NewspaperClass rhs) {
      trCollator.setStrength(Collator.PRIMARY);
      return trCollator.compare(lhs.name,rhs.name);
   }
}

Sort

Collections.sort(your array list,new NewspaperClass());