Java how to compare Predicates
I have two prodicates :
Predicate<CategoryModel> predicate1 = NavigationCategoryModel.class::isInstance; Predicate<CategoryModel> predicate2 = BrandCategoryModel.class::isInstance; With and if statement , how can I identify which predicate am I using ? I’m trying to do something like this but obviously isn’t compiling :
if(predicate1.equals(NavigationCategoryModel.class::isInstance)){ } if(predicate1==NavigationCategoryModel.class::isInstance){ } Any hint ? I’m quite new to Java 8 lambdas
This is the code of the Pojos (simple inheritance for test purposes):
public class CategoryModel { } public class NavigationCategoryModel extends CategoryModel{ } public class BrandCategoryModel extends CategoryModel { } 
You should use test method on Predicates. And, you’ve to provide the object to perform validation instead of actual method reference
predicate.test(object) Documentation: Predicate#test
For your problem, you can test if predicate1 returns true when object is of type NavigationCategoryModel as below:
predicate1.test(new NavigationCategoryModel()) // returns true Similarly, for BrandCategoryModel, use:
predicate2.test(new BrandCategoryModel()) // returns true If you want to test that object matches either of two, you can combine both the predicates like:
predicate1.or(predicate2).test(new NavigationCategoryModel()) // returns true predicate1.or(predicate2).test(new BrandCategoryModel()) // returns true 
What you try is to find which implementation you use.
The only way is to use function test from Predicate.
true if the input argument matches the predicate, otherwise false public static void main(String args[]) { Predicate<CategoryModel> predicate1 = NavigationCategoryModel.class::isInstance; Predicate<CategoryModel> predicate2 = BrandCategoryModel.class::isInstance; System.out.println("Predicate1 isNavigation: " + isNavigation(predicate1)); System.out.println("Predicate1 isBrand: " + isBrand(predicate1)); System.out.println("--------------------------------------------------"); System.out.println("Predicate2 isNavigation: " + isNavigation(predicate2)); System.out.println("Predicate2 isBrand: " + isBrand(predicate2)); } public static boolean isNavigation(Predicate<CategoryModel> predicate){ return predicate.test(new NavigationCategoryModel()); } public static boolean isBrand(Predicate<CategoryModel> predicate){ return predicate.test(new BrandCategoryModel()); } 
Just like KunLun’s solution, but I think you should add one more condition, for example
Predicate<CategoryModel> predicate1 = NavigationCategoryModel.class::isInstance; Predicate<CategoryModel> predicate2 = BrandCategoryModel.class::isInstance; Predicate<CategoryModel> predicate1Testing = NavigationCategoryModel.class::isInstance; System.out.println("Is A NavigationCategoryModel Predicate? " + predicate1.and(predicate1Testing).test(new NavigationCategoryModel())); 
