Can streams be sorted using custom object properties?

Yes, absolutely! Sorting streams by custom object properties is one of the most common tasks in Java development. You do this by passing a Comparator to the sorted() method.

Imagine you have a User class:

class User {
    String name;
    int age;

    User(String name, int age) {
        this.name = name;
        this.age = age;
    }

    public String getName() { return name; }
    public int getAge() { return age; }
}

You can sort a list of these users in several ways:

1. Sorting by a single property

Using Comparator.comparing(), you can tell Java which property to use for the sort:

List<User> users = Arrays.asList(
    new User("Alice", 30),
    new User("Bob", 20),
    new User("Charlie", 25)
);

// Sort by Age (Ascending)
users.stream()
     .sorted(Comparator.comparing(User::getAge))
     .forEach(u -> System.out.println(u.getName())); 
// Output: Bob, Charlie, Alice

2. Sorting in Reverse Order

You can simply chain .reversed() to the comparator:

// Sort by Age (Descending)
users.stream()
     .sorted(Comparator.comparing(User::getAge).reversed())
     .forEach(u -> System.out.println(u.getName()));

3. Sorting by Multiple Properties (Chaining)

If two objects have the same value for the first property, you can provide a "tie-breaker" using .thenComparing():

// Sort by Age, then by Name if ages are equal
users.stream()
     .sorted(Comparator.comparing(User::getAge)
                       .thenComparing(User::getName))
     .forEach(u -> System.out.println(u.getName()));

Why is this better?

Before Streams and Comparator.comparing, you would have to write complex logic inside a compare(o1, o2) method with multiple if-else blocks. This new way is declarative—you are telling Java what to sort by, rather than how to perform the comparison logic.

Labby's Tip: Always make sure your custom properties (like getAge) return types that are "Comparable" (like Integer, String, or Double). Most built-in Java types already are!