Sort list of objects interms of object's name

Question

I have a Fruit model class:

public class Fruit{
   private String name;
   private String color;

   public Fruit(String name, color){
     this.name = name;
     this.color = color;
   }
   public getName(){
      return name;
   }
   public getColor(){
      return color;
   }
}

Then, I created a list of fruits:

List<Fruit> fruits = new ArrayList<Fruit>();

fruits.add(new Fruit("Orange","orange"));
fruits.add(new Fruit("Strawberry","red"));
fruits.add(new Fruit("Apple","green"));
fruits.add(new Fruit("Banana","yellow"));

Now, I would like to sort the fruits elements in alphabetical order in terms of fruit name . How can I efficiently sort the fruits list?

hmjd · Accepted Answer · 2012-05-14 10:46:16Z

3

You can use Collections.sort(), defining a Comparator. For example:

Collections.sort(
    fruits,
    new Comparator<Fruit>()
    {
        public int compare(Fruit f1, Fruit f2)
        {
            // Ignore case for alphabetic ordering.
            return f1.getName().compareToIgnoreCase(f2.getName());
        }
    });

edited May 14, 2012 at 10:46

answered May 14, 2012 at 10:33

hmjd

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Comments

sarwar026 · Accepted Answer · 2012-05-14 11:03:06Z

2

use the following

Collections.sort(fruits);

public class Fruit implements Comparable {

    public int compareTo(Object o) {            
        Fruit f = (Fruit) o;
        return this.getName().compareTo(f.getName());
    }

}

edited May 14, 2012 at 11:03

answered May 14, 2012 at 10:33

sarwar026

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5 Comments

Greg Kopff Over a year ago

He needs to implement Comparable too (or supply a custom Comparator).

Leem.fin Over a year ago

I would like to compare in terms of fruit.name, that's sort the list in name's alphabetical order. how should it be compared?

Leem.fin Over a year ago

You should use "... implements Comparable<Fruit>", otherwise, it is fine

sarwar026 Over a year ago

Is it really necessary to write Comparable<Fruit>? I have worked without using the class name. But I have change the compareTo() method slightly. If after modification of that, it's still not working, then please add the Comparable<Fruit>. Thanks

Heiko Schmitz Over a year ago

Although implementing Compararable works fine, I'd prefer the alternative solution of defining a Comparator (explained in the next answer). The idea of the Comparable interface is to define some kind of "natural order", and alphabetical order is not really natural for Fruits. However, it's all a matter of taste.

Nick · Accepted Answer · 2012-05-14 10:35:19Z

1

Implement the comparable interface on the fruit class, and use Collections.sort(list) http://docs.oracle.com/javase/6/docs/api/java/lang/Comparable.html

answered May 14, 2012 at 10:35

Nick

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Comments

Alex Stybaev · Accepted Answer · 2012-05-14 10:43:42Z

0

public Comparator<Fruit> fruitComparator = new Comparator<Fruit>() {
        @Override
        public int compare(Fruit f1, Fruit f2) {

            return f1.getName().compareTo(f2.getName());
        }
    };

and then:

Collections.sort(fruits, fruitComparator );

answered May 14, 2012 at 10:43

Alex Stybaev

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Comments

Michael Schnerring · Accepted Answer · 2012-05-14 11:00:58Z

0

public class Fruit implements Comparable<Fruit> {
{
   public int compareTo(Fruit f) {
       if (this.Name == f.Name)
           return 0;
       else if (this.Name > f.Name)
           return 1;
       else
           return -1;
    }
}

Use it like this:

Collections.sort(fruits);

edited May 14, 2012 at 11:00

answered May 14, 2012 at 10:37

Michael Schnerring

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1 Comment

Tom Hawtin - tackline Over a year ago

I'm not sure it's a great idea for fruits to have a forced natural ordering.

Afshin Moazami · Accepted Answer · 2013-11-26 00:02:37Z

0

You can use a comparator. For documentation take a look at http://docs.oracle.com/javase/7/docs/api/java/util/Comparator.html

edited Nov 26, 2013 at 0:02

Afshin Moazami

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answered May 14, 2012 at 10:34

Subir Kumar Sao

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