java-8

问题 I got this little code to test out Callable . However, I find it pretty confusing how the Compiler could know if the Lambda is for the Interface Callable or Runnable since both don't have any parameter in their function. IntelliJ, however, shows that the Lambda employs the code for a Callable. public class App { public static void main(String[] args) throws InterruptedException { ExecutorService executorService = Executors.newCachedThreadPool(); executorService.submit(() ->{ System.out

问题 I got this little code to test out Callable . However, I find it pretty confusing how the Compiler could know if the Lambda is for the Interface Callable or Runnable since both don't have any parameter in their function. IntelliJ, however, shows that the Lambda employs the code for a Callable. public class App { public static void main(String[] args) throws InterruptedException { ExecutorService executorService = Executors.newCachedThreadPool(); executorService.submit(() ->{ System.out

问题 I got this little code to test out Callable . However, I find it pretty confusing how the Compiler could know if the Lambda is for the Interface Callable or Runnable since both don't have any parameter in their function. IntelliJ, however, shows that the Lambda employs the code for a Callable. public class App { public static void main(String[] args) throws InterruptedException { ExecutorService executorService = Executors.newCachedThreadPool(); executorService.submit(() ->{ System.out

问题 Consider Below 2 examples. 1 With Streams myList.stream().map(this::getInt).max(Integer::compareTo); 2 Old way int max = Integer.MIN_VALUE; for (MyItem item : myList) { max = Math.max(max, getInt(item)); } Above getInt method accepts a MyItem argument and returns an int result. Here, #2 gives me a much lower latency compared to #1. Does anyone have an idea why or anything going wrong for me? 回答1: myList.stream().mapToInt(this::getInt).max() Try mapping to an IntStream. An IntStream works with

问题 Consider Below 2 examples. 1 With Streams myList.stream().map(this::getInt).max(Integer::compareTo); 2 Old way int max = Integer.MIN_VALUE; for (MyItem item : myList) { max = Math.max(max, getInt(item)); } Above getInt method accepts a MyItem argument and returns an int result. Here, #2 gives me a much lower latency compared to #1. Does anyone have an idea why or anything going wrong for me? 回答1: myList.stream().mapToInt(this::getInt).max() Try mapping to an IntStream. An IntStream works with

问题 This question already has answers here : Is mapToDouble() really necessary for summing a List<Double> with Java 8 streams? (3 answers) Closed 4 years ago . Im trying to Figure out how to Sum up all the elements of an 'ArrayList'. Ive tried already: double totalevent = myList.stream().mapToDouble(f -> f).sum(); while myList is a ArrayList<Double> . is there a way to do it without the useless mapToDouble function? 回答1: The mapToDouble call is not useless: it performs an implicit unboxing.

问题 This question already has answers here : Is mapToDouble() really necessary for summing a List<Double> with Java 8 streams? (3 answers) Closed 4 years ago . Im trying to Figure out how to Sum up all the elements of an 'ArrayList'. Ive tried already: double totalevent = myList.stream().mapToDouble(f -> f).sum(); while myList is a ArrayList<Double> . is there a way to do it without the useless mapToDouble function? 回答1: The mapToDouble call is not useless: it performs an implicit unboxing.

问题 I want to stream the lines contained in files but MOVING each file to another folder once it has been processed. The current process is like this: Explanation: I create a Stream of Files I create a BufferedReader for each one of them I flatMap to the lines Stream of the BufferedReader I print each line. Code (omited Exceptions for simplicity): (1) Stream.generate(localFileProvider::getNextFile) (2) .map(file -> new BufferedReader(new InputStreamReader(new FileInputStream(file)))) (3) .flatMap

问题 Question Are the Java 8 java.util.Base64 MIME Encoder and Decoder a drop-in replacement for the unsupported, internal Java API sun.misc.BASE64Encoder and sun.misc.BASE64Decoder ? What I think so far and why Based on my investigation and quick tests (see code below) it should be a drop-in replacement because sun.misc.BASE64Encoder based on its JavaDoc is a BASE64 Character encoder as specified in RFC1521 . This RFC is part of the MIME specification... java.util.Base64 based on its JavaDoc Uses

问题 Installing java8 with Homebrew seems to no longer be working. After running: brew install caskroom/cask/java8 I get the following error: Error: Cask 'java8' is unavailable: '/usr/local/Homebrew/Library/Taps/caskroom/homebrew-cask/Casks/java8.rb' does not exist. Simply doing: brew cask install java8 Errors out with: Error: Cask 'java8' is unavailable: No Cask with this name exists. This seems like a recent development because I remember installing it this way a few months ago. Any suggestions