Using compareTo in an Enum

Question

I have seen this code, an am unsure how it works with the compareTo. Could someone guide me through how it works?

public enum Test
{
    POTATO("Potato"), 
    TOMATO("Tomato"), 
    CARROT("Carrot")

    public String Name;

    private Test(String name) {
        this.Name = name;
    }

    public boolean testFor(Test t)
    {
        if (compareTo(t) <= 0) {
            return true;
        }
        return false;
    }
}

Read [this](http://www.tutorialspoint.com/java/lang/enum_compareto.htm) — Jens, Dec 11 '14 at 07:10

score 7 · Accepted Answer · edited Dec 11 '14 at 07:14

7

Enum values are compared by the order they are created. So POTATO is less than CARROT because the ordinal is less for POTATO than for CARROT.

A few examples:

Test.POTATO.compareTo(Test.TOMATO); // returns -1, is less
Test.POTATO.compareTo(Test.POTATO); // returns 0, is equal
Test.CARROT.compareTo(Test.POTATO); // returns 2, is bigger

edited Dec 11 '14 at 07:14

chrylis -cautiouslyoptimistic-

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answered Dec 11 '14 at 07:11

Reuben Sanders

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Those examples that you have, do they have to be in the Enum, or can they be in any Class? – the133448 Dec 11 '14 at 07:42
You can call them from any class, as long as you import `Test`. If you want to use `compareTo(T)` in another class you have to implement the `Comparable` interface. It lets you specify a natural ordering for the class. See: https://docs.oracle.com/javase/tutorial/collections/interfaces/order.html – Reuben Sanders Dec 11 '14 at 07:59

score 0 · Answer 2 · answered Dec 11 '14 at 07:13

0

compareTo is the final method from the Enum abstract class. According to this docs

compareTo(E o) : Compares this enum with the specified object for order.

answered Dec 11 '14 at 07:13

Phat H. VU

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Using compareTo in an Enum

2 Answers2