Custom Comparator in PriorityQueue

A Custom Comparator in Java is an interface that defines a method for comparing two objects. It allows us to specify a custom sort for elements that do not have a natural order or when we want to override the default sort. Using a Comparator, we can provide our logic to compare items in a PriorityQueue and determine their priority.

Steps to Implement a Custom Comparator

Follow these steps to create a customized comparison for a specific element type in a PriorityQueue in Java.

• Create a class that implements the Comparator interface and specifies the element type we want to compare. Let’s call this class GFG.
• Use the comparison method from the Comparator interface of the GFG class.
  • This method takes two parameters representing the elements to be compared and returns an integer value based on the comparison result. The returned value must follow this rule.
  • Returns a negative integer if the first element should be greater than the first.
  • If the first element should be redundant, a positive integer is returned.
  • Returns zero if the elements have the same priority.
• Create an instance of PriorityQueue and pass an instance of the GFG class to its constructor. This will cause PriorityQueue to use our custom comparison according to object order.
• Add elements to the PriorityQueue using the add or offer method. A custom comparator is used to determine the order of the items in the queue.

PriorityQueue in Java is a data structure that stores elements according to their specified natural order or comparison. By default, it uses a natural order, but we can also define customized comparisons to sort things out based on specific criteria.