Can it be improved further? - java-8

Question

I am new to java8. Just wanted to know, this is correct way to write java 8 and suggest if given code can be improved further with respect to java8 functional programming?
public class OperationByJava8 {
public int add(int a, int b) {
Operation op = (num1, num2) -> num1 + num2;
return op.operate(a, b);
}
public int subtract(int a, int b) {
Operation op = (num1, num2) -> num1 - num2;
return op.operate(a, b);
}
public int multiply(int a, int b) {
Operation op = (num1, num2) -> num1 * num2;
return op.operate(a, b);
}
public int devide(int a, int b) {
Operation op = (num1, num2) -> {
if (num2 == 0) {
throw new IllegalArgumentException("denominator cannot be zero");
}
return num1 / num2;
};
return op.operate(a, b);
}
public static void main(String[] args) {
OperationByJava9 op = new OperationByJava9();
System.out.println(" Addition(12, 12) :" + op.add(12, 12));
System.out.println(" Subtract(12, 12) :" + op.subtract(12, 12));
System.out.println(" Multiply(12, 12) :" + op.multiply(12, 12));
System.out.println(" Devide (12, 12) :" + op.devide(12, 12));
}
}
#FunctionalInterface
interface Operation {
int operate(int a, int b);
}

Answer 1

Your approach is completely fine and would be good to proceed with.
if you want to further reduce the code, you could create a single function as follows for addition, subtraction and multiplication.
public int apply(int a, int b, IntBinaryOperator func) {
return func.applyAsInt(a, b);
}
but then you'll need to create a separate function for the division functionality in order to throw the IllegalArgumentException exception in the case of the second argument being 0.
Note that i've used the IntBinaryOperator functional interface to avoid having to create the Operation interface but if the latter is more meaningful then you can keep that.
Alternatively, you can define the functions inline and then invoke them:
IntBinaryOperator add = (num1, num2) -> num1 + num2;
IntBinaryOperator subtract = (num1, num2) -> num1 + num2;
IntBinaryOperator multiply = (num1, num2) -> num1 + num2;
IntBinaryOperator division = (num1, num2) -> {
if (num2 == 0)
throw new IllegalArgumentException("denominator cannot be zero");
return num1 / num2;
};
System.out.println(" Addition(12, 12) :" + add.applyAsInt(12, 12));
System.out.println(" Subtract(12, 12) :" + subtract.applyAsInt(12, 12));
System.out.println(" Multiply(12, 12) :" + multiply.applyAsInt(12, 12));
System.out.println(" Devide (12, 12) :" + division.applyAsInt(12, 12));