How do I sort an ArrayList of Objects, allowing user to select which parameter to sort by primarily, and secondarily?

Question

Here is what my class looks like.

public class Data {
    private int stateCode;
    private int countyCode;
    private String stateName;
    private String countyName;
    private int count1992;
    private int count1997;
    private int count2002;
    private int count2007;

    public Data(int stateCode, int countyCode, String stateName, String countyName, int count1992, int count1997, int count2002, int count2007){
        this.stateCode = stateCode;
        this.countyCode = countyCode;
        this.stateName = stateName;
        this.countyName = countyName;
        this.count1992 = count1992;
        this.count1997 = count1997;
        this.count2002 = count2002;
        this.count2007 = count2007;
    }

}

I have an ArrayList of these objects, but the user needs to select which to sort by, both primarily and secondarily. Also, both need to be sorted either ascending or descending.

I'm having trouble with how to sort this Arraylist; I'm not sure whether it will be needed to be sorted by a String or and int. Also, I'm not sure how I can choose two class parameters and sort by them. Hopefully my question makes sense. Thanks.

What is your question, how to have your user select from options, or how to sort by two fields? — khelwood, Nov 28 '20 at 22:40
how to sort by two fields! And how to change the fields for when I want to sort it. — owam, Nov 28 '20 at 23:38
[How to sort by two fields in Java?](https://stackoverflow.com/q/4805606/3890632) — khelwood, Nov 28 '20 at 23:58

score 1 · Answer 1 · edited Nov 28 '20 at 23:56

1

Use a Comparator:

Collections.sort(list, new Comparator<Data>() {
    @Override
    public int compare(Data a, Data b) {
        // code goes here
        // a < b -> return -1
        // a == b -> return 0
        // a > b -> return 1
    }
});

You can change what compare() logic is based off of the user input.

Hope this works!

edited Nov 28 '20 at 23:56

Basil Bourque

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answered Nov 28 '20 at 22:35

null_awe

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How do I sort an ArrayList of Objects, allowing user to select which parameter to sort by primarily, and secondarily?

1 Answers1