Lambda Expression java

June 8, 2022

I want to return a – b if a > b and b – a if b > a. How do I do that with a lambda expression? I already tried Calculation calculation = (a, b) -> a – b; and () -> a – b;. I know that this isn’t the desired solution yet but I already get a compilation error when trying this and I don’t know how to fix it. "variable a is already defined in method" or "incompatible types".

interface Calculator {
  public int calculate(int a, int b);
}

class Taschenrechner {
  private int doCalculation(int a, int b, Calculation calculation) {
    return calculation.calculate(a, b);
  }
  
  public int difference(int a, int b) {
    Calculation calculation = 
    return doCalculation(a, b, calculation);
  }
}

>Solution :

interface Calculator {
  public int calculate(int a, int b);
}

public class Taschenrechner {

  private int doCalculation(int a, int b, Calculator calculation) {
    return calculation.calculate(a, b);
  }
  
  public int difference(int a, int b) {
    return doCalculation(a, b, (x,y) -> x > y ? x - y : y - x);
  }

  public static void main(String...args) {
    System.out.println(new Taschenrechner().difference(7, 10));
  }
}

You can inline the lambda, all it needs is to conform with method signature from the interface