How to find an object in an ArrayList by property

In Java8 you can use streams:

public static Carnet findByCodeIsIn(Collection<Carnet> listCarnet, String codeIsIn) {
    return listCarnet.stream().filter(carnet -> codeIsIn.equals(carnet.getCodeIsin())).findFirst().orElse(null);
}

Additionally, in case you have many different objects (not only Carnet) or you want to find it by different properties (not only by cideIsin), you could build an utility class, to ecapsulate this logic in it:

public final class FindUtils {
    public static <T> T findByProperty(Collection<T> col, Predicate<T> filter) {
        return col.stream().filter(filter).findFirst().orElse(null);
    }
}

public final class CarnetUtils {
    public static Carnet findByCodeTitre(Collection<Carnet> listCarnet, String codeTitre) {
        return FindUtils.findByProperty(listCarnet, carnet -> codeTitre.equals(carnet.getCodeTitre()));
    }

    public static Carnet findByNomTitre(Collection<Carnet> listCarnet, String nomTitre) {
        return FindUtils.findByProperty(listCarnet, carnet -> nomTitre.equals(carnet.getNomTitre()));
    }

    public static Carnet findByCodeIsIn(Collection<Carnet> listCarnet, String codeIsin) {
        return FindUtils.findByProperty(listCarnet, carnet -> codeIsin.equals(carnet.getCodeIsin()));
    }
}

You can't without an iteration.

Option 1

Carnet findCarnet(String codeIsIn) {
    for(Carnet carnet : listCarnet) {
        if(carnet.getCodeIsIn().equals(codeIsIn)) {
            return carnet;
        }
    }
    return null;
}

Option 2

Override the equals() method of Carnet.

Option 3

Storing your List as a Map instead, using codeIsIn as the key:

HashMap<String, Carnet> carnets = new HashMap<>();
// setting map
Carnet carnet = carnets.get(codeIsIn);

If you use Java 8 and if it is possible that your search returns null, you could try using the Optional class.

To find a carnet:

private final Optional<Carnet> findCarnet(Collection<Carnet> yourList, String codeIsin){
    // This stream will simply return any carnet that matches the filter. It will be wrapped in a Optional object.
    // If no carnets are matched, an "Optional.empty" item will be returned
    return yourList.stream().filter(c -> c.getCodeIsin().equals(codeIsin)).findAny();
}

Now a usage for it:

public void yourMethod(String codeIsin){
    List<Carnet> listCarnet = carnetEJB.findAll();

    Optional<Carnet> carnetFound = findCarnet(listCarnet, codeIsin);

    if(carnetFound.isPresent()){
        // You use this ".get()" method to actually get your carnet from the Optional object
        doSomething(carnetFound.get());
    }
    else{
        doSomethingElse();
    }
}

Here is a solution using Guava

private User findUserByName(List<User> userList, final String name) {
    Optional<User> userOptional =
            FluentIterable.from(userList).firstMatch(new Predicate<User>() {
                @Override
                public boolean apply(@Nullable User input) {
                    return input.getName().equals(name);
                }
            });
    return userOptional.isPresent() ? userOptional.get() : null; // return user if found otherwise return null if user name don't exist in user list
}