Sorting ArrayList to rearrange by a specific string

Question

I'm trying to rearrange my ArrayList by a specific string. so I'd like to rearrange my list by giving a priority to the type "truck" than the type "sedan" or the type "SUV". Technically, I could use reverseorder from their alphabetical order but I'd like to implement where a specific string itself has the priority. For example, if I have a list of cars in random order as following,

ArrayList<Car> cars = new ArrayList<Car>(Arrays.asList(
new Car("1", "truck"), 
new Car("2", "sedan"), 
new Car("3", "SUV"), 
new Car("4", "truck"), 
new Car("5", "truck"));

so that my ideal order should be 1,4,5,2,3. I appreciate any ideas!

See also the tutorial on method references: https://docs.oracle.com/javase/tutorial/java/javaOO/methodreferences.html — markspace, Jul 24 '21 at 22:22
Hmm, now I have to ask. Do you not know how to use comparators (which is what the duplicate link explains) or do you specifically not know how to get a comparator to sort in your desired order? — markspace, Jul 24 '21 at 22:28

score 0 · Accepted Answer · answered Jul 24 '21 at 22:25

0

You can sort based on the index in a List.

List<String> order = Arrays.asList("truck", "sedan", "SUV");
cars.sort(Comparator.comparingInt(c -> order.indexOf(c.getType()));

answered Jul 24 '21 at 22:25

Unmitigated

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The OP says "giving a priority to the type "truck" than the type "sedan" or the type "SUV"" so what they want is actually a sort that does not go in lexical order. – markspace Jul 24 '21 at 22:27
@markspace My solution does not sort in lexicographical order. – Unmitigated Jul 24 '21 at 22:29
That's kind of what was requested... – Zevrant Jul 24 '21 at 22:34
@Zevrant What do you mean? – Unmitigated Jul 24 '21 at 22:34
Mis reasread my bad – Zevrant Jul 24 '21 at 22:37

score 0 · Answer 2 · answered Jul 24 '21 at 22:29

Just of the top of my head,l. First for the 'types' I would create an enum of all of your types that has the property 'priority' (an integer maybe). If this is a custom class you wrote/have access to edit I would implement the comparable interface on the car class after you change the class so the 'type' uses the enum instead of the string. As long as the enum matches the string given you can use the search method to match the string against the enum name( not sure if case sensitive), see here for a good example on how to implement the comparable interface https://www.javatpoint.com/Comparable-interface-in-collection-framework. Then implement compare to based on the enumeration priority value.

Sorting ArrayList to rearrange by a specific string

2 Answers2