I have a list of objects say car. I want to filter this list based on some parameter using Java 8. But if the parameter is null, it throws NullPointerException. How to filter out null values? Current code is as follows requiredCars = cars.stream().filter(c -> c.getName().startsWith(“M”)); This throws NullPointerException if getName() returns null. 6 Answers … Read more
I want to collect the items in a stream into a map which groups equal objects together, and maps to the number of occurrences. List<String> list = Arrays.asList(“Hello”, “Hello”, “World”); Map<String, Long> wordToFrequency = // what goes here? So in this case, I would like the map to consist of these entries: Hello -> 2 … Read more
In Java 8, there is a new method String.chars() which returns a stream of ints (IntStream) that represent the character codes. I guess many people would expect a stream of chars here instead. What was the motivation to design the API this way? 2 Answers 2
I was testing out some new features of Java 8 and copied the example into my IDE (Eclipse originally, then IntelliJ) as shown here Eclipse offered no support whatsoever for lambda expressions, and IntelliJ kept reporting an error Lambda expressions not supported at this language level I would like to know if this is a … Read more
I have a list myListToParse where I want to filter the elements and apply a method on each element, and add the result in another list myFinalList. With Java 8 I noticed that I can do it in 2 different ways. I would like to know the more efficient way between them and understand why … Read more
While hunting through some code I came across the arrow operator, what exactly does it do? I thought Java did not have an arrow operator. return (Collection<Car>) CollectionUtils.select(listOfCars, (arg0) -> { return Car.SEDAN == ((Car)arg0).getStyle(); }); Details: Java 6, Apache Commons Collection, IntelliJ 12 Update/Answer: It turns out that IntelliJ 12 supports Java 8, which … Read more
I have installed JDK 8 and trying to run Eclipse. I am getting following warning message: Java HotSpot(TM) 64-Bit Server VM warning: ignoring option MaxPermSize=512m; support was removed in 8.0 What are the reasons for ignoring this VM option? 6 Answers 6
I’m using java lambda to sort a list. how can I sort it in a reverse way? I saw this post, but I want to use java 8 lambda. Here is my code (I used * -1) as a hack Arrays.asList(files).stream() .filter(file -> isNameLikeBaseLine(file, baseLineFile.getName())) .sorted(new Comparator<File>() { public int compare(File o1, File o2) { … Read more
I need to consume a web service in my project. I use NetBeans so I right-clicked on my project and tried to add a new “Web Service Client”. Last time I checked, this was the way to create a web service client. But it resulted in an AssertionError, saying: java.lang.AssertionError: org.xml.sax.SAXParseException; systemId: jar:file:/path/to/glassfish/modules/jaxb-osgi.jar!/com/sun/tools/xjc/reader/xmlschema/bindinfo/binding.xsd; lineNumber: 52; … Read more
Unlike C#’s IEnumerable, where an execution pipeline can be executed as many times as we want, in Java a stream can be ‘iterated’ only once. Any call to a terminal operation closes the stream, rendering it unusable. This ‘feature’ takes away a lot of power. I imagine the reason for this is not technical. What … Read more
