Java按数学顺序打印出所有数字

Question

I want the program to print out every number that each digit to the power to 3 added together will equal that number. For instance, the number 153: 1^3 + 5^3 + 3^3 = 153.

This is the code, but I do not know why it does not work.

Edit: The reason I have siffra++; is because I want it to test all numbers to 500 . This is what I got now, but it does still now work (not showing anything in JOptionPane ):

int siffra = 153;

String allaSiffror = "";
int count = 0;

if (siffra < 500) { 
    for (int i = 0; i < 3; i++) {
        String siffran = Integer.toString(siffra);
        String selekt = siffran.substring(i,i+1);
        int selekta = Integer.parseInt(selekt);
        count += Math.pow(selekta,3);
            if (count == siffra) {
                System.out.println(count);
                allaSiffror += count + " ";
                count = 0;
            } 
            siffra++;
    }
}


JOptionPane.showMessageDialog(null, allaSiffror);

Answer 1

the problem is that this part is outside of the loop:

String siffran = Integer.toString(siffra);
int count = 0;

so your count adds up every number to the previous, and since you increase siffra but work on siffran- you're checking 100 all the time

aside from that, I'd also take @Sluth's advice - no need to convert back and forth to string and int - use mathematical mod and % to get the digits

Answer 2

Such numbers are called Armstrong numbers
Firstly your mistakes
1) Your are making count(sum I assumed) 0 only if you find number matching your condition like 153...what if number is not matching then shouldn't the count/sum be zero for new number.
2) Secondly you are saying that, you want to test numbers till 500 but you are using if condition which would be exectued only once ...so use loop over there

Few suggestions I would make
1)Instead of using String use StringBuilder.
2)Also instead of converting integer to string and then using substring directly work with integer only

So modify code as follows

 int siffra = 153;

 StringBuilder allaSiffror = new StringBuilder();
 int count;

 while(siffra<500){
     count = 0;
     int temp = siffra;

     int num;
     while(temp>0){
       num=temp%10;  
       temp=temp/10;
       count += Math.pow(num,3);  
     }

     if (count == siffra){
       System.out.println(count);
       allaSiffror.append(count + " ");
     } 
     siffra++;
 }
System.out.println(allaSiffror.toString());


JOptionPane.showMessageDialog(null, allaSiffror.toString());

Update o/p is as follows :

 153 370 371 407 153 370 371 407