Getting NullPointerException when trying to stream().filter().collect(Collectors.toList())) on Java list

Question

I got a problem while trying to search a specific Java object in a list.
Actually i got the search function i want working for another Java class. Now i tried it for a different one but instead of returning a list of results i get a NullPointerException.

This is how my function looks:

 public static List<Customer> searchByEverything(String keyword){
    List<Customer> customerList = find.all(); //Using java Ebean

    System.out.println(keyword); //Check if keyword is not empty
    System.out.println(customerList); //Check if list is not empty

    Predicate<Customer> customerPredicate = u -> u.name.toLowerCase().contains(keyword.toLowerCase());

    try{
        return customerList.stream().filter(customerPredicate).collect(Collectors.toList());
    }catch (Exception e){
        e.printStackTrace();
    }

This is the strack trace from Exception e:

java.lang.NullPointerException
at models.Customer.lambda$searchByEverything$2(Customer.java:174)
at java.util.stream.ReferencePipeline$2$1.accept(ReferencePipeline.java:174)
at java.util.ArrayList$Itr.forEachRemaining(ArrayList.java:891)
at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
at java.util.stream.ReduceOps$ReduceOp.evaluateSequential(ReduceOps.java:708)
at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
at java.util.stream.ReferencePipeline.collect(ReferencePipeline.java:499)
at models.Customer.searchByEverything(Customer.java:179)
at controllers.Application.searchCustomers(Application.java:262)
at router.Routes$$anonfun$routes$1$$anonfun$applyOrElse$17$$anonfun$apply$17.apply(Routes.scala:479)
at router.Routes$$anonfun$routes$1$$anonfun$applyOrElse$17$$anonfun$apply$17.apply(Routes.scala:479)
at play.core.routing.HandlerInvokerFactory$$anon$4.resultCall(HandlerInvoker.scala:157)
at play.core.routing.HandlerInvokerFactory$$anon$4.resultCall(HandlerInvoker.scala:156)
at play.core.routing.HandlerInvokerFactory$JavaActionInvokerFactory$$anon$14$$anon$3$$anon$1.invocation(HandlerInvoker.scala:136)
at play.core.j.JavaAction$$anon$1.call(JavaAction.scala:73)
at play.http.HttpRequestHandler$1.call(HttpRequestHandler.java:54)
at play.mvc.Security$AuthenticatedAction.call(Security.java:53)
at play.core.j.JavaAction$$anonfun$7.apply(JavaAction.scala:108)
at play.core.j.JavaAction$$anonfun$7.apply(JavaAction.scala:108)
at scala.concurrent.impl.Future$PromiseCompletingRunnable.liftedTree1$1(Future.scala:24)
at scala.concurrent.impl.Future$PromiseCompletingRunnable.run(Future.scala:24)
at play.core.j.HttpExecutionContext$$anon$2.run(HttpExecutionContext.scala:56)
at play.api.libs.iteratee.Execution$trampoline$.execute(Execution.scala:70)
at play.core.j.HttpExecutionContext.execute(HttpExecutionContext.scala:48)
at scala.concurrent.impl.Future$.apply(Future.scala:31)
at scala.concurrent.Future$.apply(Future.scala:492)
at play.core.j.JavaAction.apply(JavaAction.scala:108)
at play.api.mvc.Action$$anonfun$apply$2$$anonfun$apply$5$$anonfun$apply$6.apply(Action.scala:112)
at play.api.mvc.Action$$anonfun$apply$2$$anonfun$apply$5$$anonfun$apply$6.apply(Action.scala:112)
at play.utils.Threads$.withContextClassLoader(Threads.scala:21)
at play.api.mvc.Action$$anonfun$apply$2$$anonfun$apply$5.apply(Action.scala:111)
at play.api.mvc.Action$$anonfun$apply$2$$anonfun$apply$5.apply(Action.scala:110)
at scala.Option.map(Option.scala:146)
at play.api.mvc.Action$$anonfun$apply$2.apply(Action.scala:110)
at play.api.mvc.Action$$anonfun$apply$2.apply(Action.scala:103)
at scala.concurrent.Future$$anonfun$flatMap$1.apply(Future.scala:251)
at scala.concurrent.Future$$anonfun$flatMap$1.apply(Future.scala:249)
at scala.concurrent.impl.CallbackRunnable.run(Promise.scala:32)
at akka.dispatch.BatchingExecutor$AbstractBatch.processBatch(BatchingExecutor.scala:55)
at akka.dispatch.BatchingExecutor$BlockableBatch$$anonfun$run$1.apply$mcV$sp(BatchingExecutor.scala:91)
at akka.dispatch.BatchingExecutor$BlockableBatch$$anonfun$run$1.apply(BatchingExecutor.scala:91)
at akka.dispatch.BatchingExecutor$BlockableBatch$$anonfun$run$1.apply(BatchingExecutor.scala:91)
at scala.concurrent.BlockContext$.withBlockContext(BlockContext.scala:72)
at akka.dispatch.BatchingExecutor$BlockableBatch.run(BatchingExecutor.scala:90)
at akka.dispatch.TaskInvocation.run(AbstractDispatcher.scala:39)
at akka.dispatch.ForkJoinExecutorConfigurator$AkkaForkJoinTask.exec(AbstractDispatcher.scala:415)
at scala.concurrent.forkjoin.ForkJoinTask.doExec(ForkJoinTask.java:260)
at scala.concurrent.forkjoin.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1339)
at scala.concurrent.forkjoin.ForkJoinPool.runWorker(ForkJoinPool.java:1979)
at scala.concurrent.forkjoin.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:107)

As i said, i have exactly the same search implemented for a different class and it works perfectly fine. Both customerList and keyword are not empty. The only difference between searching in my customerList and the other list, is that it has around 4500 objects with around 50 attributes per object. Maybe that's the problem?

Thank you in advance!

Solution

Very likely u.name is null

Try to change your Predicate in

Predicate<Customer> customerPredicate = u -> (u.name != null && u.name.toLowerCase().contains(keyword.toLowerCase()));

To see what's the Customer instance that has name == null, you could add a peek method in your chain.

customerList.stream()
.peek(c -> { 
   if (c.name == null) {
      // do something...
   }
}).filter(customerPredicate).collect(Collectors.toList());

Comments

[nbokmans]

While this question will 100% get closed as duplicate of "What is a NPE" question, could you post this line: at models.Customer.lambda$searchByEverything$2(Customer.java:17‌​4) (so line 174)

[Alberto S.]

Maybe there are some users whose name attribute is null

[Abubakkar]

Just a side-note, you can also use parallelStream (might improve performance stackoverflow.com/documentation/java/88/streams/2785/…)

[f1sh]

@nbokmans that's the lambda itself. The lambda's code is part of the question.

[Elias Johannes]

Sorry if this is a duplicate... i'm really overstrained with this problem. @nbokmans As f1sh says, this line is the definition of the lambda expression.

[Elias Johannes]

While i'm not getting a NullPointerException anymore, it returns all of the objects now. You are probably right that u.name is null, but i can't figure out why?

[freedev]

@EliasJohannes I've updated my answer.

[Elias Johannes]

Thank you, this did the job. probably really was that there were null references in the DB.