Using Lambda expression, I want to sort by integer values using the Java language

Question

Using Lambda expression, I want to sort integer values using the Java language

public class Test_LAMBDA_Expression {

public static void main(String[] args) {

    List<Test_Product> list= new ArrayList<Test_Product>();

    list.add(new Test_Product(1,"HP Laptop",25000f));  
    list.add(new Test_Product(2,"Keyboard",300f));  
    list.add(new Test_Product(2,"Dell Mouse",150f));
    list.add(new Test_Product(4,"Dell PC",150f));
    list.add(new Test_Product(5,"Dell Printer",150f));


    System.out.println("Sorting by name");

    Collections.sort(list,(p1,p2)->{
        return p1.name.compareTo(p2.name);
    });

    for(Test_Product p: list){
        System.out.println(p.id+" "+p.name+" "+p.price);
     }
  }

}

Now I want to sort using id. How can I do that?

Possible duplicate of java 8, Sort list of objects by attribute without custom comparator — Draken
– Draken, Commented May 22, 2017 at 8:23

Thomas Fritsch · Accepted Answer · 2017-05-22 08:16:20Z

5

You can use (assuming id is an int):

Collections.sort(list, Comparator.comparingInt(p -> p.id));

answered May 22, 2017 at 8:16

Thomas Fritsch

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2 Comments

Anonymous Over a year ago

Why complicate it more than this? It is not only simpler and shorter than the other answers, it is also less errorprone.

Holger Over a year ago

Or list.sort(Comparator.comparingInt(p -> p.id));, but both will end up at the same code in recent JREs.

ΦXocę 웃 Пepeúpa ツ · Accepted Answer · 2017-05-22 08:00:41Z

3

you can use a lambda and get the id to compare those elements in the list

list.sort((x, y) -> Integer.compare(x.getId(), y.getId()));
System.out.println(list);

answered May 22, 2017 at 8:00

ΦXocę 웃 Пepeúpa ツ

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Comments

Ted Cassirer · Accepted Answer · 2017-05-22 08:01:26Z

3

Like so:

  Collections.sort(list,(p1,p2)->Integer.compare(p1.id, p2.id));

answered May 22, 2017 at 8:01

Ted Cassirer

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