Pass Lambda Expression as Method Parameter in Java

A lambda expression is an anonymous or unnamed method in Java. It doesn't execute on its own and used to implement methods that are declared in a functional interface. If we want to pass a lambda expression as a method parameter in java, the type of method parameter that receives must be of functional interface type.

Example

interface Algebra {
   int operate(int a, int b);
}
enum Operation {
   ADD, SUB, MUL, DIV
}
public class LambdaMethodArgTest {
   public static void main(String[] args) {
      print((a, b) -> a + b, Operation.ADD);
      print((a, b) -> a - b, Operation.SUB);
      print((a, b) -> a * b, Operation.MUL);
      print((a, b) -> a / b, Operation.DIV);
   }
   static void print(Algebra alg, Operation op) {
      switch (op) {
         case ADD:
            System.out.println("The addition of a and b is: " + alg.operate(40, 20));
            break;
         case SUB:
            System.out.println("The subtraction of a and b is: " + alg.operate(40, 20));
            break;
         case MUL:
            System.out.println("The multiplication of a and b is: " + alg.operate(40, 20));
            break;
         case DIV:
            System.out.println("The division of a and b is: " + alg.operate(40, 20));
            break;
         default:
            throw new AssertionError();
      }
   }
}

Output

The addition of a and b is: 60
The subtraction of a and b is: 20
The multiplication of a and b is: 800
The division of a and b is: 2