Java equivalent of Where Clause in C# Linq

Question

I can do this in C# :

int CheetahNumber = 77; Animal Cheetah = Model.Animals    .Where(e => e.AnimalNo.Equals(CheetahNumber))    .FirstOrDefault(); 

For example in Java I have ArrayList<Animal> Animals

How can I query such an ArrayList? Thanks.

Answer 1

Java 8 introduces the Stream API that allows similar constructs to those in Linq.

Your query for example, could be expressed:

int cheetahNumber = 77;  Animal cheetah = animals.stream()   .filter((animal) -> animal.getNumber() == cheetahNumber)   .findFirst()   .orElse(Animal.DEFAULT); 

You'll obviously need to workout if a default exists, which seems odd in this case, but I've shown it because that's what the code in your question does.

Answer 2

You can try it by using streams:

public String getFirstDog(List<Animal> animals) {     Animal defaultDog = new Dog();     Animal animal = animalNames.stream(). //get a stream of all animals          filter((s) -> s.name.equals("Dog")).findFirst(). //Filter for dogs and find the first one         orElseGet(() -> defaultDog ); //If no dog available return an default animal.                                         //You can omit this line.     return animal; }