Question

I have question regarding Java Comparator. Or maybe you all have another Idea to solve this problems.

I have object called Product, below the Product Class looks like:

public class Product(){
   private String productId;
   private List categoryList;

   //...setter and getter for category List
}

Then I have a list of Product, List. And I want to sort the list based on the category of Product:

Here example of the List:

{
    Product = {
        productId:10000567,
        categoryList: {1002, 1003, 1007}
    },
    Product = {
        productId:10000568,
        categoryList: {1001, 1003, 1007}
    },
    Product = {
        productId:10000569,
        categoryList: {1001, 1004, 1007}
    },
    Product = {
        productId:10000570,
        categoryList: {1004, 1005, 1007}
    }
}

I already try to use comparator, but I only can compare one value for one time.
Thanks for your response.

Answer 1

First, let your class Product implement the interface Comparable, then implement compareTo(), then sort the List with Collections.sort(myList);

public class Product implements Comparable<Product>{
   private String productId;
   private List categoryList;

  //...setter and getter for category List

   public int compareTo(Product p) {
       //return -1, 0 or 1 based on what you decide makes p to be less than this
   }

}

//sort it
java.util.Collections.sort(myProductList);