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BiPredicate List::contains  RSS feed

 
Greenhorn
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Hi guys , i am Levent ,
I am preparing OCP8 for upgrade my OCP6 certificate.

As you know ;



how can be this code valid ?
0)contains method is not static.
boolean contains(Object o)

1) and method should be like ;
boolean contains(Object  , Object)
boolean contains(List , Integer)



A Comprehensive OCPJP 8 Certication Guide



Thank you.
 
Sheriff
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Before Java 8 you would create this anonymous class to do exactly the same

And to fix your compiler error, you need something like

So the method signature of your static containsTwo method is actually containsTwo(List<Integer> list, Integer num) (if you try to switch these parameter types, you'll get a compiler error).
 
Master Rancher
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What helped me when it comes to understanding method references was to write out lambda's with explicit parameters. Once I got the hang of that, it turned out to be relatively easy to start understanding and using method references. For instance, have a look at a simplified version of your class. At first I use lambda's with explicit parameters, that gives me a clue how many parameters are involved. Then it is easy to write equivalent versions that use method references. See if this makes sense:
 
Saloon Keeper
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Piet Souris wrote:What helped me when it comes to understanding method references was to write out lambda's with explicit parameters.


Good advice for those of us, like me, who need to know about lambdas and the Predicate interface for the OCA 1Z0-808 exam.

Thanks.
 
Levent Erguder
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