Java: do while wont while

Question

    Anfallare.armees = 10;
    Forsvarare.armees = 10;
 do{
    Anfallare.slaTarningar();
    Forsvarare.slaTarningar();

    Anfallare.visaTarningar();
    Forsvarare.visaTarningar();

    MotVarandra(Anfallare, Forsvarare);

    status(Anfallare, Forsvarare);

    }while(Anfallare.armees == 0 || Forsvarare.armees == 0);

is what I have, I tried also a

 System.out.println(Anfallare.armees + " :: " + Forsvarare.armees);

after this do while and it is 9 and 10, neither of them are 0.

Why does it run this once?

Stevi Deter · Accepted Answer · 2011-05-25 21:35:48Z

7

Because, as you point out, after the first run, Anfallare.armees is 9, which does not equal 0, and Forsvarare.armees is 10, which is not equal to 0.

Perhaps you meant

while(Anfallare.armees != 0 && Forsvarare.armees != 0)

answered May 25, 2011 at 21:35

Stevi Deter

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Comments

James · Accepted Answer · 2012-01-07 01:59:45Z

4

while(Anfallare.armees == 0 || Forsvarare.armees == 0)

Means continue only if Anfallare.armees == 0 || Forsvarare.armees == 0. In your example, neither is 0 so it will not loop.

while(Anfallare.armees != 0 && Forsvarare.armees != 0)

Means, stop looping if either are zero (Anfallare.armees != 0 && Forsvarare.armees != 0)

You may actually be wanting:

while (Anfallare.armees != 0 || Forsvarare.armees != 0)

means, stop looping if both are 0

edited Jan 7, 2012 at 1:59

user212218

answered May 25, 2011 at 21:42

James

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Comments

jontro · Accepted Answer · 2011-05-25 21:49:20Z

3

You need to do

while(Anfallare.armees != 0 || Forsvarare.armees != 0);

To make it loop until both of those variables are 0

edited May 25, 2011 at 21:49

answered May 25, 2011 at 21:36

jontro

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Comments

Community · Accepted Answer · 2017-05-23 12:19:59Z

2

Because you start as do{}, which forces to execute at least once the code, and then you have while x==0, which is not true. Since it is not true, the loop ends.

As you see in the other answers, you may need to check for x != 0 (not equal to), or even better x>0 (in the event x could take a negative number)

Take some time to read the Oracle's Java tutorials I linked in the other answer to you. It explains the loop logic very well.

edited May 23, 2017 at 12:19

CommunityBot

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answered May 25, 2011 at 21:37

Aleadam

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Comments

Péter Török · Accepted Answer · 2011-05-25 21:38:37Z

2

If I understand you correctly, your do-while loop body is executed once, but you think it shouldn't have run at all - is this correct?

The reason is, in do-while the loop condition is checked only after the loop body is executed. I.e. it will always run at least once.

answered May 25, 2011 at 21:38

Péter Török

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Comments

finnw · Accepted Answer · 2011-05-25 21:36:08Z

1

It's hard to tell without the complete code, but it may be that you just need to invert the condition:

}while(!(Anfallare.armees == 0 || Forsvarare.armees == 0));

answered May 25, 2011 at 21:36

finnw

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Comments

Lukas Knuth · Accepted Answer · 2011-05-25 21:37:53Z

1

You condition says ... as long as one of them is 0. What you'll want is this:

while(Anfallare.armees > 0 || Forsvarare.armees > 0);

answered May 25, 2011 at 21:37

Lukas Knuth

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Comments

Jason Rogers · Accepted Answer · 2011-05-25 21:47:23Z

1

the reason is simple

while loops when the expression is true.

so what you want is

while(Anfallare.armees != 0 || Forsvarare.armees != 0);

but even better I would suggest

while(Anfallare.armees > 0 || Forsvarare.armees > 0);

this would allow you to be sure that your armee count never gets negative ^^

Jason

answered May 25, 2011 at 21:47

Jason Rogers

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