sort students name by province

[jaque322]

i have an arraylist, that stores objects from a class called prematricula and every object stored has name and province how i can do to pass the name of the province and the method return the names of the students sorted alfabethically...
please if someone can help me....

[peter_budo]

Create method that will take an ArrayList as an agrument and will have ArrayList as return value. Something along the line of this method showed by masijade in this thread

[kvprajapati]

Use java.lang.Comparable interface and java.util.Arrays class.

Here is sample code:

Emp.java

public class Emp implements Comparable
{
  private String name;
  private String city;

  public Emp(){}
  public Emp(String name,String city) { 
        this.city=city; this.name=name;}
  public int compareTo(Object p)
  {
     Emp a=(Emp)p;
     return name.compareTo(a.name);
  }
  public String getName() { return name;}
  public String getCity() { return city;}
}

and
Sort2.java

import java.util.*;

public class Sort2
{
  public static void main(String []args)  
  {
     ArrayList<Emp> a=new ArrayList<Emp>();
     a.add(new Emp("Amar","Zar"));
     a.add(new Emp("Zalar","Ara"));
     a.add(new Emp("Bab","Ac"));
     a.add(new Emp("Japp","rc"));

     Object []arr=a.toArray();
     Arrays.sort(arr);
     List b=Arrays.asList(arr);
    // Print elements
     for(int i=0;i<b.size();i++)
      {
         Emp k=(Emp)b.get(i);
         System.out.println(k.getName() + " " + k.getCity());
      }
     // Another way to print elements
      for(Iterator e=b.iterator();e.hasNext();)
      {
        Emp k=(Emp)e.next();
        System.out.println(k.getName() + " " + k.getCity());
      }
  }
}

[masijade]

Yes, as long as it's not JME implementing Comparable or creating a Comparator is the way to go, but there is no reason to use Arrays. Collections also has sort methods. No reason to convert to an array and back to a list, leave it as a list.

[kvprajapati]

I am sorry. Which collection class has sort method?

[masijade]

I am sorry. Which collection class has sort method?

Collections

That is a Class in and of itself, much like Arrays.

[kvprajapati]

Thanks masijade.

I appreciate your help.

Thanks again.

[peter_budo]

If I was on chapter 7 of SCJP study guide I would have answered correctly ;) , but I'm only chapter 3 :$

[masijade]

If I was on chapter 7 of SCJP study guide I would have answered correctly ;) , but I'm only chapter 3 :$

Technically, you were correct, and, in fact, that way may even be quicker than using the Collections manner, it's just longer to write, and not quite as "code reusable". ;)

[jaque322]

thanks to everybody