Two objects supplier

Question

I have a binary function:

public Integer binaryFunction(Integer a, Integer b){
    //some stuff
}

And I have this stream:

Integer fixedValue = ...
List<Integer> otherValues = ...
otherValues.map(value -> binaryFunction(value, fixedValue)).collect(...);

I would like to know how can I use map(this::binaryFunction) in my stream. I tried something like this but it won't work:

values.map(value -> (value, fixedValue)).map(this::binaryFunction).collect(...);

But it does not work. I'm looking for a supplier that can take two values.

Note: I don't want to change binaryFunction declaration.

Answer 1

You can't do this. You must use the lambda you have shown.

You could write a function that modifies binary functions to fix their first argument, but its body is just going to be the same lambda.

Answer 2

The only way you can do this if you have fixedValue as a class level variable and you dont need to supply it in the function. In other words

public class Foo {
    private Integer fixedValue;


    public Integer binaryFunction(Integer a) {
        //use fixedValue (as it is class variable)
        //some stuff
    }

    public void doSomeThing() {
        this.fixedValue = ...//setting fixed value here
        List<Integer> otherValues = ...
        otherValues.map(this::binaryFunction)...
    }
}