how to pass function to method parameter in java

Question

APIResponse res = kpiAPIObject.getALLKPIDefinition(); --> function a

Boolean status = res.getNodeValues("shortName").contains(kpiName); --> function b

public void dynamicWait(function a,function b)
{
    long t = System.currentTimeMillis();
    while (t > System.currentTimeMillis() - 180000 ) {
        res = /* execute function a here */
        if(/* execute function b here */) {
            break;
        } else {
            Thread.sleep(30000);
            continue;
        }
    }  
}

Thanks in advance

if(res.getNodeValues("shortName").contains(kpiName)) {}

Julez
– Julez

2019-01-11 05:40:58 +00:00
Commented Jan 11, 2019 at 5:40 — Julez
– Julez, Commented Jan 11, 2019 at 5:40

shmosel · Accepted Answer · 2019-01-11 05:43:06Z

3

Sounds like you could use some lambdas:

Supplier<APIResponse> a = kpiAPIObject::getALLKPIDefinition;
Predicate<APIResponse> b = res -> res.getNodeValues("shortName").contains(kpiName);

Then call them like:

APIResponse res = a.get();
if (b.test(res)) {
    break;
}

answered Jan 11, 2019 at 5:43

shmosel

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5 Comments

Patrick Over a year ago

And the method signature would look something like: public <T> void dynamicWait(Supplier<T> a, Predicate<T> b)

shmosel Over a year ago

In which case the first line would be T res = a.get();.

Srikanta Over a year ago

Lambda expression's parameter res cannot redeclare another local variable defined in an enclosing scope. in Predicate<APIResponse> b = res -> res.getNodeValues("shortName").contains(kpiName);

shmosel Over a year ago

@Srikanta So rename res to something else.

Srikanta Over a year ago

still get the error ...Lambda expression's parameter res cannot redeclare another local variable defined in an enclosing scope.

mkjh · Accepted Answer · 2019-01-11 06:11:54Z

3

In Java, there are various ways. If you take a look at java.util.function package, you can see

Function: Takes one argument, produces one result
Consumer: Takes one argument, produces nothing.
BiConsumer: Takes two arguments, produces nothing.
Supplier: Takes no argument, produces one result.
Predicate: Boolean value function of one argument

You can used them as inputs for your method and execute it within.

In you case, you will use Supplier for function a and Predicate for function b.

Supplier<APIResponse> a = () -> { return kpiAPIObject.getALLKPIDefinition(); }; Predicate<APIResponse> b = res -> res.getNodeValues("shortName").contains(kpiName);

public void dynamicWait(Supplier<APIResponse> a,Predicate<APIResponse> b)

{

long t = System.currentTimeMillis();

while (t > System.currentTimeMillis() - 180000 ){

            res = a.get();
            if(b.test(res)){
                break;
            }
            else{
                Thread.sleep(30000);
                continue;
            }
        }  

}

edited Jan 11, 2019 at 6:11

answered Jan 11, 2019 at 5:52

mkjh

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4 Comments

Srikanta Over a year ago

Lambda expression's parameter res cannot redeclare another local variable defined in an enclosing scope. in Predicate<APIResponse> b = res -> res.getNodeValues("shortName").contains(kpiName);

mkjh Over a year ago

@Srikanta rename it to something else like response

Srikanta Over a year ago

still get the error ...Lambda expression's parameter res cannot redeclare another local variable defined in an enclosing scope.

mkjh Over a year ago

@Srikanta change to Predicate<APIResponse> b = response -> response.getNodeValues("shortName").contains(kpiName);

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