I need to get two separate lines for evens and odds, but the catch is, I can use only one while loop

Question

This is my code:

int numb = 50;
int odd;
int even;
while (numb <= 100) {
    if (numb % 2 == 0) {
        even = numb;
        System.out.println(even);
        System.out.print(", ");
        numb++;
    }
    System.out.println("");
    if (numb % 2 != 0) {
        odd = numb;
        System.out.print(odd);
        System.out.print(", ");
        numb++;
    }
}

So far, it prints two columns of answers but i need to separate rows of evens and odds. What am I doing wrong?

Why not just add the evens and odds in two separate arrays or lists, and then print these two arrays/lists at the end, after the while-loop ends? — Chthonic Project, Sep 25 '17 at 15:36
I cannot use arrays, i'd love to but cannot. That is a condition of this program in a whole. — The Captain, Sep 25 '17 at 15:38
@ChthonicProject printing this array/list in a good format would probably require another loop. Simplest way would be to just use two Stringbuilders where you append the evens/odds and print those after the while loop is done. — OH GOD SPIDERS, Sep 25 '17 at 15:38
you don't need the second if, you can just use else. also, numb++ doesn't need to be repeated - you're going to do that whatever the result of the if statement. and, you don't really need variables odd and even. — pecks, Sep 25 '17 at 15:39
@pecks I tried removing the second if and used an else, it made me remove the print statement to separate the lines. How else can have that line separation? — The Captain, Sep 25 '17 at 15:42
@OHGODSPIDERS The toString() method in Java 8 already uses StringBuilder to do this. For older versions, your argument is correct. — Chthonic Project, Sep 25 '17 at 15:45

Ravi · Accepted Answer · 2017-09-25T15:47:22.447

4

You can use two StringBuilder and keep appending sOdd and sEven to respective StringBuilder and after the loop you can print them.

Something similar

StringBuilder sOdd = new StringBuilder("");
StringBuilder sEven = new StringBuilder("");

while (numb <= 100) {
    if (numb % 2 == 0) {
        sEven.append(numb).append(",");
    }
    if (numb % 2 != 0) {
        sOdd.append(numb).append(",");
    }
   numb++;
}

System.out.println(sEven.toString()+"\n"+sOdd.toString());

edited Sep 25 '17 at 15:47

answered Sep 25 '17 at 15:38

Ravi

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Why using the "String", if we can use other mutable string classes like "StringBuilder" or "StringBuffer". – Punit Sep 25 '17 at 15:43
@Punit true. As OP was not specific. I can change it, if you wish ;) – Ravi Sep 25 '17 at 15:43
Perfect, that is running perfectly, I did not know that strings can work that way. I am a low intermediate java user so it is good to know they can work as such. – The Captain Sep 25 '17 at 15:45

score 0 · Answer 2 · answered Sep 25 '17 at 15:52

I f you're particular about single while loop and constant extra space you can do this:

int numb1 = 50,numb2=51;
while (numb1 <= 100 || numb2<=100) 
{
if (numb1<=100) 
{
    System.out.print(numb1);
    System.out.print(", ");
    numb1=numb1+2;
}


else if (numb2<=100) 
{
    if(numb2==51)
    System.out.println();

    System.out.print(numb2);
    System.out.print(", ");
    numb2=numb2+2;
}
}

I need to get two separate lines for evens and odds, but the catch is, I can use only one while loop

2 Answers2