Greenfoot

erdelf wrote ...

2012/10/16

simple problem with switch-case

erdelf

2012/10/16

following code:

            switch(Greenfoot.getRandomNumber(2))
            {
                case 0: var++;
                case 1: var--;
            }

the variable is only changed when 1 returns;

SPower

2012/10/16

You forgot the break statements at the end of each case, which causes the switch to execute both cases when the result is 0.

Duta

2012/10/16

You need:

switch()
{
    case 0:
        var++;
        break;
    case 1:
        var--;
}

Otherwise if the case is 0, var gets incremented but without the break statement it flows into the following case, which decrements var, meaning overall it looks like it hasn't changed. On a side note, there are better ways to do this than using a switch, for example:

import java.util.Random;
if(new Random().nextBoolean())
    var++;
else
    var--;

or if you really want to use Greenfoot.getRandomNumber() for some reason...:

if(Greenfoot.getRandomNumber(2) == 0)
    var++;
else
    var--;

erdelf

2012/10/16

thx SPower, I always forget this

SPower

2012/10/16

@Duta btw this:

import java.util.Random;  
if(new Random().nextBoolean())  
    var++;  
else  
    var--;

won't work, this:

import java.util.Random;  
if((new Random()).nextBoolean())  
    var++;  
else  
    var--;

will :)

danpost

2012/10/16

Either one of the following would work:

var = var - 1 + 2 * Greenfoot.getRandomNumber(2);
// OR
var = var + 1 - 2 * Greenfoot.getRandomNumber(2);

which are equivalent to

var -= 1 - 2 * Greenfoot.getRandomNumber(2);
// OR
var += 1 - 2 * Greenfoot.getRandomNumber(2);

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simple problem with switch-case