CODEWITHSUNDEEP
java
None
None

Reputation: 9247

Order by some property nulls first?

I have List of some objects. And i want to order by some property and nulls first, such as in query:

select * from aaa order by ext_id nulls first;

I know when i have list of string i can do this:

   List<String> names2 = Arrays.asList("XML", null, "Java", "HTML", "CSS");
    names2.sort(Comparator.nullsFirst(String::compareTo));

But what when i have List of some objects of class?

Any suggestion how can i achive that in java?

Upvotes: 0

Views: 238

Answers (1)

Maksim Bezmen
Maksim Bezmen

Reputation: 88

You can do that, for example:

public static void main(String[] args) {
        A a1 = new A();
        a1.setName("A");
        A a2 = new A();
        a2.setName("B");
        A anull = null;
    List<A> list = new ArrayList<>();
    list.add(a1);
    list.add(a2);
    list.add(anull);
    list.sort(nullsFirst(
            comparing(A::getName, nullsFirst(naturalOrder()))));
    list.forEach(System.out::println);

}

public static class A {
    String name;

    public String getName() {
        return name;
    }

    public void setName(final String name) {
        this.name = name;
    }
}

Upvotes: 1

Related Questions