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stream.filter is not working for some objects in my List<Objects>, is there any solution or other method? [closed]

Edit the question to include desired behavior, a specific problem or error, and the shortest code necessary to reproduce the problem . This will help others answer the question.

Closed 1 year ago .

I made a filter for a list of Objects and searching for the name of one objects in this list: tables.getTable().stream().filter(p->p.geName().equals(referenceName)).findAny;

The referenceName is not null and also the object that contains this name exist in the list, but it results an error, here is the result:

java.lang.NullPointerException at comparator.complex.obj.comparison.XmlObjComparison.lambda$XmlObjectsComparison$8(XmlObjComparison.java:359) java.base/java.util.stream.MatchOps$1MatchSink.accept(MatchOps.java:90) java.base/java.util.ArrayList$ArrayListSpliterator.tryAdvance(ArrayList.java:1632) java.base/java.util.stream.ReferencePipeline.forEachWithCancel(ReferencePipeline.java:127) java.base/java.util.stream.AbstractPipeline.copyIntoWithCancel(AbstractPipeline.java:502) java.base/java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:488) java.base/java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:474) java.base/java.util.stream.MatchOps$MatchOp.evaluateSequential(MatchOps.java:230) java.base/java.util.stream.MatchOps$MatchOp.evaluateSequential(MatchOps.java:196) java.base/java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234) java.base/java.util.stream.ReferencePipeline.noneMatch(ReferencePipeline.java:538) comparator.complex.obj.comparison.XmlObjComparison.XmlObjectsComparison(XmlObjComparison.java:359) comparator.complex.obj.comparison.XmlObjComparison.test2(XmlObjComparison.java:584) java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.base/java.lang.reflect.Method.invoke(Method.java:566) at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50) org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12) org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47) org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17) at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325) at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78) org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57) at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290) at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71) at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288) at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58) at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268) at org.junit.runners.ParentRunner.run(ParentRunner.java:363) at org.junit.runner.JUnitCore.run(JUnitCore.java:137) at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:69) com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:33) com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235) at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)

what is possible? because in some cases it works and in some others it does not work!

You should use Stream::peek to debug the application and use additional filters or null check:

tables.getTable() // some collection
    .stream()
    .peek(p -> System.out.println("1: p=" + Objects.toString(p))) // 
    .filter(Objects::nonNull) // make sure p is not null
    .peek(p -> System.out.println("2: p.name=" + Objects.toString(p.getName()))) // 
    .filter(p -> Objects.equals(referenceName, p.getName()))
    .findAny();
Mere null check
tables.getTable() // some collection
    .stream()
    .filter(p -> p != null && Objects.equals(referenceName, p.getName()))
    .findAny();
tables.getTable().stream().filter(p->p.geName().equals(referenceName)).findAny;
It must be p.geName() returning null. Try either Objects.equals(referenceName, p.geName()) or referenceName.equals(p.geName()) or put in a null check. Also, I assume that findAny is a method call but you excluded the parenthesis. Just to clarify: I'm not saying that p is null, but that the result of p.geName() might be null. If it is, then calling .equals() on it will obviously yield a NullPointerException.
If your problem is still not solved, you're going to have to provide more information, like how you are creating the stream, what you are trying to do, what the p variable even is and the structure of p's class.
                unfortunately it is not working still, p.getName() is not a null ! the objects is a List<Object> Object contains many Values that one of them is 'Name' when I use the get(index) it gave me the correct value (when you know the index) like  tables.getTable.get(index).getName() it is working and giving the correct value! but when I put this in the streaming it return an error! it is so wierd for me!
– anf
                Dec 17, 2021 at 19:50