Java Hashcode and Equals for Java 8 Functional Interface Objects

Question

I have a code that looks like this:

import java.util.ArrayList;
import java.util.List;
import java.util.function.Function;

class MyObj {
    private final Double aDouble;

    public MyObj(Double aDouble) {
        this.aDouble = aDouble;
    }
}

class Main {
    public static void main(String[] args) {
        List<Function<MyObj, String>> functionList1 = new ArrayList<>();
        List<Function<MyObj, String>> functionList2 = new ArrayList<>();

        // ... Add same Function<MyObj, String>s to both lists

        // I want to assert that functionList1.equals functionList2
    }
}

I would check that some Function, Supplier, BiFunctionor something else that may be MyObj, will be equal to the other, if the result of the call Function/ Supplieretc returns the same value with the same input.

So, in this case, Java compares the values ​​of two lists with equals, for example, functionList1.get(0).apply(standardInstanceOfMyObj)equal functionList2.get(0).apply(standardInstanceOfMyObj), etc.

My question is, how can I override equalsand hashcodeto a certain type, for example Function<MyObj, String>, to do the work above?

Answer 1

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