如何按ID排序此对象 [英] How do I sort this object by id

问题描述

我有这段代码。我的比较器是否正确？



公共抽象类人员实现可比较< person> {

private int _id;

private int _phoneNumber;

private String _name;

private List< notification> _listNotifications;



@Override

public int compareTo（Person p）{

return this.getId（） .compareTo（p.getId（））;

}



我的尝试：



我试图编译并检查它是否有效但是它不起作用

I have this piece of code. Is my comparator correct?

public abstract class Person implements Comparable<person> {
private int _id;
private int _phoneNumber;
private String _name;
private List<notification> _listNotifications;

@Override
public int compareTo(Person p){
return this.getId().compareTo(p.getId());
}

What I have tried:

I was trying to compile and checks if it works but it is not working

推荐答案

试试

Try

class Person implements Comparable<Person>
{
  private int _id;
  private String _name;

  public int getId(){ return _id;}
  public String getName(){ return _name; }

  Person( int id, String name){ _id = id; _name = name; }

  @Override
  public int compareTo(Person p)
  {
    return Integer.compare(this.getId(), p.getId());
  }


  public static void main( String arg[])
  {
    Person p1 = new Person( 12,  "Boo");
    Person p2 = new Person( 10,  "Foo");

    String is = p1.compareTo(p2) > 0  ? "is" : "is not ";

      System.out.printf("%s %s bigger than %s", p1.getName(), is, p2.getName());
  }
}

[update]

遵循请求...

[update]
Following the kind request...

import java.util.*;

class Person implements Comparable<Person>
{
  private int _id;
  private String _name;

  public int getId(){ return _id;}
  public String getName(){ return _name; }

  Person( int id, String name){ _id = id; _name = name; }

  @Override
  public int compareTo(Person p)
  {
    return Integer.compare(this.getId(), p.getId());
  }


  public static void main( String arg[])
  {
    Person p1 = new Person( 12,  "Boo");
    Person p2 = new Person( 10,  "Foo");

    ArrayList <Person> alp=new ArrayList<Person>();
    alp.add(p1);
    alp.add(p2);

    Collections.sort(alp);

    for ( Person p : alp)
      System.out.printf("%s\n", p.getName());

    Collections.sort( alp, new NameComparator() );

    for ( Person p : alp)
      System.out.printf("%s\n", p.getName());
  }
}

class NameComparator  implements Comparator<Person>
{
 @Override
    public int compare(Person p1, Person p2) {
        return p1.getName().compareTo(p2.getName());
    }
}

[/ update]

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