java-8

问题 While reading the documentation about streams, I came across the following sentences: ... attempting to access mutable state from behavioral parameters presents you with a bad choice ... if you do not synchronize access to that state, you have a data race and therefore your code is broken ... [1] If the behavioral parameters do have side-effects ... [there are no] guarantees that different operations on the "same" element within the same stream pipeline are executed in the same thread. [2]

问题 Sonar tells me "Replace this lambda with a method reference" public class MyClass { private List<SomeValue> createSomeValues(List<Anything> anyList) { return anyList // .stream() // .map(anything -> createSomeValue(anything)) // .collect(Collectors.toList()); } private SomeValue createSomeValue(Anything anything) { StatusId statusId = statusId.fromId(anything.getStatus().getStatusId()); return new SomeValue(anything.getExternId(), statusId); } } Is this possible here? I tried several things,

问题 From this Number of String Objects on stack overflow,I came to know that if we do some thing like : String s = new String("ABC"); Then we have two objects one on heap that is String and one on constant pool that is "ABC" , But today I took the heap dump and found there are two objects on heap it self. I used MAT tool for the same please find the screen shot below. So my query is if there are two Objects on heap one of Char[] and other for String class and one on constant pool then thus this

问题 From this Number of String Objects on stack overflow,I came to know that if we do some thing like : String s = new String("ABC"); Then we have two objects one on heap that is String and one on constant pool that is "ABC" , But today I took the heap dump and found there are two objects on heap it self. I used MAT tool for the same please find the screen shot below. So my query is if there are two Objects on heap one of Char[] and other for String class and one on constant pool then thus this

问题 I tried to run 100 Sleep tasks in parallel using Java8(1.8.0_172) stream.parallel() submitted inside a custom ForkJoinPool with 100+ threads available. Each task would sleep for 1s. I expected the whole work would finish after ~1s, given the 100 sleeps could be done in parallel. However I observe a runtime of 7s. @Test public void testParallelStream() throws Exception { final int REQUESTS = 100; ForkJoinPool forkJoinPool = null; try { // new ForkJoinPool(256): same results for all tried

问题 I have a string 2017-07-31T01:01:00-07:00 and I am trying to parse it to date and in CST Timezone. I am getting different results when i parse this string using Date and Java 8 ZonedDateTime. I am not getting why this is happening and what I am doing wrong. String dateStr = "2017-07-31T01:01:00-07:00"; LocalDateTime time = null; SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd'T'HH:mm:ss-hh"); String[] dateArray = dateStr.split("-"); String[] timeZones = TimeZone .getAvailableIDs

问题 I have a String like 101-1-5,101-2-4,102-1-5,102-2-5,102-3-5,103-1-4 . I want to add this in to a Map<String, Map<String, String>> . Like: {101={1=5, 2=4}, 102={1=5, 2=5, 3=5}, 103={1=4}} How to do this using Java 8 stream? I tried using normal Java. And it works fine. public class Util { public static void main(String[] args) { String samp = "101-1-5,101-2-4,102-1-5,102-2-5,102-3-5,103-1-4"; Map<String, Map<String, String>> m1 = new HashMap<>(); Map<String, String> m2 = null; String[] items

问题 I'm having a problem in writing an algorithm to help me scan a file system and find all subclasses of a certain class. Details: I've an app that scans an external application using nio Files.walk() while retrieving I check for "extends SuperClass" while reading the file if the word exits, I add the class name in my list as follows: List<String> subclasses = new ArrayList<>(); Files.walk(appPath) .filter(p->Files.isRegularFile(p) && p.toString() .endsWith(".java")).forEach(path -> { try { List

问题 I have a running app spring boot 1.3 + hibernate 5 + java 8 + ZonedDateTime + postgresql and in one of the tables I have the following fields. @Column(name = "DATE_ENABLED") @Type(type="java.time.ZonedDateTime") private ZonedDateTime dateEnabled; @Column(name = "DATE_DISABLED") @Type(type="java.time.ZonedDateTime") private ZonedDateTime dateDisabled; If I run the app then I see that this by default produces "timestamp without time zone" testDB=# \d type Table "public.type" Column | Type |

问题 I have the following code: Set<Integer> l = new TreeSet<>(); l.add(1); l.add(10); l.add(3); l.add(-3); l.add(-4); and I want to unorder the collection with: l.stream().unordered().forEach(System.out::println); but the forEach returns always the collection ordered! Then I have also another doubt about this sentence: For sequential streams, the presence or absence of an encounter order does not affect performance, only determinism. If a stream is ordered, repeated execution of identical stream