Mathematical operations with an operator variable - Java

Question

I have two variables of type int (called int1 and int2) and a variable type char (which always saves a mathematical operator and is called op). How can I do mathematical operations with these three variables? I have to do it manually, I can not use ScriptEngineManager for teacher's reasons

I can not do int res = int1 + op + int2 because it adds the value that the variable op has in the ascii table. How could I put these three variables together to do a mathematical operation according to the variable op?

The simplest way I have found to do it is the following:

int res = 0;
if (op == '+'){res=int1+int2;}
else if (op == '-'){res = int1-int2;}
else if (op == '*'){res = int1*int2;}
else {res = int1/int2;}

Is there any more elegant way than this? Thank you!

The answer is No there isn't. You could use a switch statement rather than if/else, but you still need a separate branch for each operator. — Stephen C, Apr 17 '18 at 03:50
Looks to me like you are on the right track. Keep going & keep up the good work. — Robert Dodier, Apr 17 '18 at 04:19

Frans Henskens · Answer 1 · 2018-04-17T06:03:59.910

Create an enumeration that maps the operation character to a function of two ints.

enum Operator {
    ADD('+',(x,y)->x+y),
    SUBTRACT('-',(x,y)->x-y),
    MULTIPLY('*',(x,y)->x*y),
    DIVIDE('/',(x,y)->x/y),
    REMAINDER('%',(x,y)->x%y),
    POW('^',(x,y)->(int)Math.pow(x,y));

    char symbol;
    BiFunction<Integer,Integer,Integer> operation;

    Operator(final char symbol, final BiFunction<Integer,Integer,Integer> operation) {
        this.symbol = symbol;
        this.operation = operation;
    }

    public static Operator representedBy(final char symbol)
    {
        return Stream.of(Operator.values()).filter(operator->operator.symbol==symbol).findFirst().orElse(null);
    }

    public Integer apply(final int x,final int y)
    {
        return operation.apply(x,y);
    }
}

public static void main(final String[] args) {
    final char op = '+';
    final int int1 = 1;
    final int int2 = 2;
    final Operator operator = Operator.representedBy(op);
    if (operator == null)
    {
        // handle bad character
    }
    else
    {
        System.out.println(operator.apply(int1,int2));
    }
}

Mathematical operations with an operator variable - Java

1 Answers1