Apply Function to while loop in Java

Question

I have while loop which is supposed to run while condition1 is true or while condition2 is true. 1 or 2 case depends on some initial boolean condition.

Now I implemented this as a ternary operator, but I'd like to understand how this can be done using a Predicate, and lambda expressions. Can someone provide an example please? How can I declare a Function variable and put it into the while loop condition?

boolean initialCondition = stopBtn.getText().length() > 0;

while(initialCondition ? stopBtn.waitToBeHidden() : stopBtn.isDisplayed()) {
    if (a++ < 5) {
        stopBtn.click();
    }
}
return this;

Could you show some pseudo-code of what you want to achieve? I don't quite know where you want to apply a predicate... — randers
– randers, Commented Feb 15, 2016 at 16:48

Dennis Hunziker · Accepted Answer · 2016-02-15 16:56:23Z

5

I think even in a predicate you'd need your if/else.

If you provide more code it would probably be easier to see what you're aiming to do. One way of using a predicate (that you can then pass around etc.) would be:

Predicate<StopBtnClass> pred = btn -> btn.getText().length() > 0 ? btn.waitToBeHidden() : btn.isDisplayed();

while(pred.test(stopBtn)) {
    ...

answered Feb 15, 2016 at 16:56

Dennis Hunziker

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1 Comment

Bohdan Nesteruk Over a year ago

Yes, I understand regarding if/else in predicate. I just confused when tried to apply predicate in 'while' condition. I forgot about .test(...) method. But your example works great for me, than you!

wero · Accepted Answer · 2016-02-15 16:55:44Z

4

You can use a BooleanSupplier to model the condition:

java.util.function.BooleanSupplier condition = stopBtn.getText().length() > 0 ?
     stopBtn::waitToBeHidden : 
     stopBtn::isDisplayed;

while (condition.getAsBoolean()) {
    ...
}

answered Feb 15, 2016 at 16:55

wero

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