? operator on multiple ifs / cleaner code

Question

so I have this part of a code on a finished project:

        if (mode == 1) {                    
        repeats = 2;
        columns = 6;
        size = 24;
    }
    else if (mode == 2) {               
        repeats = 2;
        columns = 8;
        size = 48;
    }
    else if (mode == 3) {               
        repeats = 3;
        columns = 6;
        size = 36;
    }

I'm just messing with it and I was wondering if there is a better way to write this part using the ? operator or any other way.

Answer 1

I would define an int[][] with the values for each mode as a key. Like,

int[][] modes = { {}, { 2, 6, 24 }, { 2, 8, 48 }, { 3, 6, 36 } };
if (mode > 0 && mode < 4) {
    repeats = modes[mode][0];
    columns = modes[mode][1];
    size = modes[mode][2];
}

Answer 2

Using the ternary ? operator would not work because you have too many variables that you want to update depending on the value of mode. If you used ? then you could only use it on one variable at a time and the code would be very cumbersome and hard to read. Switch is the best option

Answer 3

The best way to wipe if is using polymorphic. For your given code you can abstract a class or an interface and implement the method in different ways. The example code is like following.

public class Test {
    public static void main(String[] args) {
        int modeValue = 1;//2,3 ...
        ModeFactory modeFactory = new ModeFactory();
        Mode mode = modeFactory.generateMode(modeValue);
        mode.fillData();
        System.out.println("mode info:" + mode.toString());
    }
}

abstract class Mode {
    int repeats;
    int columns;
    int size;

    abstract void fillData();

    @Override
    public String toString() {
        return "Mode{" +
                "repeats=" + repeats +
                ", columns=" + columns +
                ", size=" + size +
                '}';
    }
}

class Mode1 extends Mode {

    @Override
    void fillData() {
        repeats = 2;
        columns = 6;
        size = 24;
    }
}

class Mode2 extends Mode {

    @Override
    void fillData() {
        repeats = 2;
        columns = 8;
        size = 48;
    }
}

class Mode3 extends Mode {

    @Override
    void fillData() {
        repeats = 3;
        columns = 6;
        size = 36;
    }
}

class ModeFactory {
    Mode generateMode(int modeValue) {
        if (modeValue == 1) {
            return new Mode1();
        }
        if (modeValue == 2) {
            return new Mode2();
        }
        return new Mode3();
    }
}

design patterns may help you solve these problem.

Answer 4

You cannot use here the ? operator, because it returns a value in each branch. In this case you can use a switch:

switch (mode) {
            case 1: 
                repeats = 2;
                columns = 6;
                size = 24;
                break;

            case 2: 
               repeats = 2;
               columns = 8;
               size = 48;
                break;

            case 3:
            case SUNDAY: 
                ...
                break;

            default:
                System.out.println("No default value");
                break;
        }

Answer 5

Best alternative of multiple if block is go via switch case. It will be more readable code.

int mode = 1;
  switch (mode) { 
        case 1:
            //your logic
            break; 
        case 2: 
             //your logic
            break; 
        case 3: 
            // your logic
            break; 
         default: 
            // When anything doesnt match 
            break; 
        } 

Answer 6

I like the if statement. Easy to read and debug. But I think enums are better suited for this type of situation. Even if it is only used in your class you can declare private enum and only use inside a single method:

     private enum Mode{
        ONE(2, 6, 24),
        TWO(2, 8 , 48),
        THREE(3, 6, 36);

        int repeats;
        int columns;
        int size;

        Mode(int repeats, int columns, int size){
            this.repeats = repeats;
            this.columns = columns;
            this.size = size;
        }

        public int getRepeats() {
            return repeats;
        }

        public int getColumns() {
            return columns;
        }

        public int getSize() {
            return size;
        }  
    }

And the nice thing is that you can use Enum.values and avoid creating separate array.

    int mode = 1;
    Mode m = Mode.values()[mode - 1]; //m will be ONE

Answer 7

Java has the switch statement which you can use like follows:

switch(mode)
     case 1:
        repeats = 2;
        columns = 6;
        size = 24;
        break;
     case 2:
        repeats = 2;
        columns = 8;
        size = 48;
        break;
     case 3:
        repeats = 3;
        columns = 6;
        size = 36;
        break;
      ...

Note: Don't forget to include the breaks in your case statements. Otherwise, the behaviour is fall through to the next case statement until it hits the end or a break.

Technically, you could use the ? operator, however it's really better to use it for 2 cases (condition is true or condition is false). You would also need to change your logic slightly. In this case it would make your code worse.

if(mode == 1) ? repeats = 2; columns = 6; size = 24 : (if(mode == 2) ? repeats = 2, columns = 8; size = 48 : (if(mode == 3) ... ) )