Sort an array with two arguments

Question

I already know how to sort an ArrayList but I wanna know if this is possible to sort an Array with two arguments like: I have an array 5 same objects with a float and a String in it like that:

- object 1 : 0 "DD"
- object 2 : 3 "FF"
- object 3 : 1 "GG"
- object 4 : 2 "AA"
- object 5 : 1 "AA"

And I want sort them like that:

- object 1 : 0 "DD"
- object 5 : 1 "AA"
- object 3 : 1 "GG"
- object 4 : 2 "AA"
- object 2 : 3 "FF"

Is it possible to sort them with a comparator by multiplying the Float.compare() and the String.compare() ? or do you need to sort them first with the Float.compare() and then create sub-arrays to compare with the String.compare() ?

A mixture of regex and sorting will suffice.Use : as the separator in String.split() and then sort those arrays using Arrays.sort()!!! — Am_I_Helpful
– Am_I_Helpful, Commented Oct 29, 2014 at 7:20

JB Nizet · Accepted Answer · 2014-10-29 07:22:54Z

3

Yes, of course. You just need a comparator that compares elements by their float value and, if their float value are equal, compares them by their string value:

public class FooComparator implements Comparator<Foo> {
    @Override
    public int compare(Foo f1, Foo f2) {
        int result = Float.compare(f1.getFloatValue(), f2.getFloatValue());
        if (result == 0) {
            result = f1.getStringValue().compareTo(f2.getStringValue());
        }
        return result;
    }
}

Java 8 can even do that for you:

Comparator<Foo> c = Comparator.comparingDouble(Foo::getFloatValue)
                              .thenComparing(Foo::getStringValue);

answered Oct 29, 2014 at 7:22

JB Nizet

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1 Comment

Ezequiel Over a year ago

+1 From Acache Commons I founded useful ChainComparator commons.apache.org/proper/commons-collections/javadocs/…

Mureinik · Accepted Answer · 2014-10-29 07:24:30Z

2

You need to define your class as Comparable:

public MyClass implements Comparable<MyClass> {
    private float f;
    private String s;

    @Override
    public int compare (MyClass other) {
       int first = Float.compare(f, other.f);
       if (first != 0) {
           return first;
       }

       return s.compare(other.s);
    }
}

And then just call Arrays.sort(myList).

answered Oct 29, 2014 at 7:24

Mureinik

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