Question

Is there a reasonable explanation, why searching an element in Java collection is so hard?
For example, let’s say I have:

ArrayList<People> listPeople = new ArrayList<People>();

public class People
{
   public String name;
   public String age;
   //some other code here
}

You got the idea … Now, if I want to get from list a Person with given name, let’s say ‘Anthares’ I have to do so much work: Create a new Person with name ‘Anthares’, probably initiate it with some other data, predefine my equals method for Person class, then call listPeople.IndexOf(tempPerson) and finally get the returned int and make listPeople[idx]

Why is all this pain. For example, in C# I can make a linq expression, pass it to the proper method of my collection and that’s it. One simple line of code.

Answer 1

No you don’t – you can do:

Person found = null;
for (Person person : listPeople)
{
    if ("Anthares".equals(person.name))
    {
        found = person;
        break;
    }
}
// Check for found == null etc

Yes, it’s still more work than LINQ, but that’s basically because C# has closures in the form of lambda expressions. You could implement something similar in Java if you were willing to write:

Person person = FakeLinq.findFirst(listPeople, new Predicate<Person>() {
    @Override boolean matches(Person person) {
        return person.name.equals("Anthares");
    }
});

Most of the conciseness of the C# solution is just allowing you to express that predicate very simply.

Java 7 will (hopefully!) have something reasonably similar to lambda expressions, at which point this becomes feasible in Java too.