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# How do you structure the do while loop for the battery exercise?

How do you structure the do while loop for the battery exercise?

GoKart.java
```public class GoKart {
public static final int MAX_ENERGY_BARS = 8;
private String mColor;
private int mBarsCount;

public GoKart(String color) {
mColor = color;
mBarsCount = 0;
}

public String getColor() {
return mColor;
}

public void charge() {
if (!isFullyCharged()) {
mBarsCount++;
//mBarsCount=MAX_ENERGY_BARS;
}

public boolean isBatteryEmpty() {
return mBarsCount == 0;
}

public boolean isFullyCharged() {
return mBarsCount == MAX_ENERGY_BARS;
}

}
```

Here is the solution to the exercise:

```    public void charge() {
while (!isFullyCharged()) {
mBarsCount++;
}
}
```

Let's walk through it. The exercise says to use your new isFullyCharged method along with the ! sign using a while loop.

So what we do here is while not (!) fully charged, or in code this is the line that reads: while (!isFullyCharged), then we get inside the loop and increment mBarsCount by one using the post-increment operator (the ++ after mBarsCount).

In this case you could use either the pre-increment operator (++mBarsCount) or the post increment. The difference is that the pre-increment operator first increments the value and then uses it in any expression, where as post-increment increments the value after any expression is evaluated. Because the increment is in its own line both yield the same results and it's as if you had done mBarsCount += 1; or mBarsCount = mBarsCount + 1;

Hope this helps, and feel free to tag me in the post or ping me via Twitter (see my profile) if you need any more help with this :D

Great job on working through the exercises and keep up the effort.