Comparable, Comparator, and Sorting
Explore how to define sorting logic in Java by implementing Comparable for natural order and using Comparator for custom orders. Understand type safety with generics, and apply sorting to custom classes. This lesson helps you build flexible and robust sorting strategies for your objects.
Java knows how to sort integers and strings automatically because their definitions include built-in rules for order: 1 comes before 2, and “A” comes before “B.” However, when we define custom types like a User or Product, Java has no inherent knowledge of which object should come first. If we try to sort a list of these objects without defining an order, the compiler will stop us.
To solve this, we must define exactly what less than or greater than means for our specific data. In this lesson, we will use the Comparable and Comparator interfaces to build robust sorting logic, relying on generics to ensure we never accidentally compare incompatible types.
Natural ordering with Comparable
The most fundamental way to define order for a class is to implement the Comparable<T> interface. This interface forces a class to define its own natural ordering, the default sequence used whenever a list of these objects is sorted.
The interface defines a single method: compareTo(T other). This method compares the current ...