java-stream

I have a text file like this: ids.txt 1000 999 745 123 ... I want to read this file and load it in a two dimensional array. I expect to have an array similar to the one below: Object[][] data = new Object[][] { // { new Integer(1000) }, // { new Integer(999) }, // { new Integer(745) }, // { new Integer(123) }, // ... }; Here is the code I wrote: File idsFile = ... ; try (Stream<String> idsStream = Files.lines(idsFile.toPath(), StandardCharsets.US_ASCII)) { Object[][] ids = idsStream .filter(s -> s.trim().length() > 0) .toArray(size -> new Object[size][]); // Process ids array here... } When

This question already has an answer here: Do terminal operations close the stream? 2 answers Consider the following code: Path directory = Paths.get(/* some directory */); Files.list(directory).forEach(System.out::println); Does a terminal operation (like forEach ) close the underlying file that has been opened? Refer to the relevant parts of the javadoc of Files.list : The returned stream encapsulates a DirectoryStream. If timely disposal of file system resources is required, the try-with-resources construct should be used to ensure that the stream's close method is invoked after the stream

This question already has an answer here: Why does Stream<T> not implement Iterable<T>? 9 answers I have this code: List<String> strings = Arrays.asList("a", "b", "cc"); for (String s : strings) { if (s.length() == 2) System.out.println(s); } I want to write it using a filter and a lambda: for (String s : strings.stream().filter(s->s.length() == 2)) { System.out.println(s); } I get Can only iterate over an array or an instance of java.lang.Iterable . I try: for (String s : strings.stream().filter(s->s.length() == 2).iterator()) { System.out.println(s); } And I get the same error. Is this even

List<Integer> integer = Stream.generate(new Supplier<Integer>() { int i = 0 ; @Override public Integer get() { return ++i; } }).filter(j -> j < 5) .limit(10) // Note the call to limit here .collect(Collectors.toList()); Counter to my expectation, the collect call never returns. Setting limit before filter produces the expected result. Why? Since there are only 4 elements that pass the filter, limit(10) never reaches 10 elements, so the Stream pipeline keeps generating new elements and feeding them to the filter, trying to reach 10 elements that pass the filter, but since only the first 4

import java.util.ArrayList; import java.util.List; public class IterationBenchmark { public static void main(String args[]){ List<String> persons = new ArrayList<String>(); persons.add("AAA"); persons.add("BBB"); persons.add("CCC"); persons.add("DDD"); long timeMillis = System.currentTimeMillis(); for(String person : persons) System.out.println(person); System.out.println("Time taken for legacy for loop : "+ (System.currentTimeMillis() - timeMillis)); timeMillis = System.currentTimeMillis(); persons.stream().forEach(System.out::println); System.out.println("Time taken for sequence stream : "+

I was wondering how stream().toArray[x -> new Integer[x]] knows what size of array to from? I wrote a snippet in which i created a list of an integer of size 4 and filtered the values and it created an array of length of the filtered stream, I could not see any method on stream to get a size of the stream. List<Integer> intList = new ArrayList<Integer>(); intList.add(1); intList.add(2); intList.add(3); intList.add(4); Integer[] array = intList.stream() .filter(x -> x > 2) .toArray(x -> { System.out.println("x --> " + x); return new Integer[x]; }); System.out.println("array length: " + array

I have below code snap with Java 8. List<Employee> employees = DataProvider.getEmployees(); Set<Employee> set = employees.stream().filter(emp -> { System.out.println(emp.getName()); return emp.getName().equals("Vishal"); }).collect(Collectors.toSet()); I just want to know which implementation of Set it is using by default when we use Collectors.toSet() (refer above example)? Also, is there any way to tell the Java API to use a particular implementation (for example, HashSet )? The toSet() collector does not specify which implementation it uses; you get a Set , that's all. If you want a