java-8

问题 There is a client that needs to serialize many lambda functions defined in the client side and send them to the server, which has to be able to correctly deserialize them. The server also have implementations of all those lambda functions in the client, but the details could be slightly different from the client-side implementations (like minor versioning differences). Given that Java Lambdas depends on compiler specific artifacts, simply serializing a lambda function to SerializedLambda and

问题 In one of my use cases I need to fetch the data from multiple nodes. Each node maintains a range (partition) of data. The goal is to read the data as fast as possible. Constraints are, cardinality of a partition is not known before hand. Using work sharing approach, I could split the partitions into sub-partitions and fetch the data in parallel. One drawback with this approach is, it is possible that one thread could fetch lot of data and take more time while the other thread could finish

问题 In one of my use cases I need to fetch the data from multiple nodes. Each node maintains a range (partition) of data. The goal is to read the data as fast as possible. Constraints are, cardinality of a partition is not known before hand. Using work sharing approach, I could split the partitions into sub-partitions and fetch the data in parallel. One drawback with this approach is, it is possible that one thread could fetch lot of data and take more time while the other thread could finish

问题 I have nested lists and I'm trying to group and sum to get the desired result using java streams and collectors . With this I'm not able to loop over multiple SubAccounts . Either I have to use for loop or some other logic. I want to achieve using streams api. Is there any possibility for that Map<Long, BigDecimal> assetQuanMap = subAccounts.getAssets.parallelStream().collect(Collectors.groupingBy(Asset::getAssetId, Collectors.reducing(BigDecimal.ZERO, Asset::getQuantity, BigDecimal::add)));

问题 I have nested lists and I'm trying to group and sum to get the desired result using java streams and collectors . With this I'm not able to loop over multiple SubAccounts . Either I have to use for loop or some other logic. I want to achieve using streams api. Is there any possibility for that Map<Long, BigDecimal> assetQuanMap = subAccounts.getAssets.parallelStream().collect(Collectors.groupingBy(Asset::getAssetId, Collectors.reducing(BigDecimal.ZERO, Asset::getQuantity, BigDecimal::add)));

问题 Is there any ceil counterpart for Math.floorDiv() How to calculate it fastest way with what we have? UPDATE The code for floorDiv() is follows: public static long floorDiv(long x, long y) { long r = x / y; // if the signs are different and modulo not zero, round down if ((x ^ y) < 0 && (r * y != x)) { r--; } return r; } Can we code ceil the similar way? UPDATE 2 I saw this answer https://stackoverflow.com/a/7446742/258483 but it seems to have too many unnecessary operations. 回答1: There is

问题 Is there any ceil counterpart for Math.floorDiv() How to calculate it fastest way with what we have? UPDATE The code for floorDiv() is follows: public static long floorDiv(long x, long y) { long r = x / y; // if the signs are different and modulo not zero, round down if ((x ^ y) < 0 && (r * y != x)) { r--; } return r; } Can we code ceil the similar way? UPDATE 2 I saw this answer https://stackoverflow.com/a/7446742/258483 but it seems to have too many unnecessary operations. 回答1: There is

问题 I'm trying to convert 2D list to a 2D int array. However, it seems I can only collect objects, not primitives. When I do: data.stream().map(l -> l.stream().toArray(int[]::new)).toArray(int[][]::new); I get the compile-time error Cannot infer type argument(s) for <R> map(Function<? super T,? extends R>) . However, if I change int[] to Integer[] , it compiles. How can I get it to just use int ? 回答1: Use mapToInt method to produce a stream of primitive integers: int[][] res = data.stream().map(l

问题 I am new in Java 8 streams and I am wondering if there is way to perform forEach/map call on method returning a byte and accepting an int as parameter. Example: public class Test { private byte[] byteArray; // example of byte array public byte getByte(int index) { return this.byteArray[index]; } public byte[] getBytes(int... indexes) { return Stream.of(indexes) .map(this::getByte) // should return byte .collect(byte[]::new); // should return byte[] } } As you may guess, the getBytes method

问题 I am new in Java 8 streams and I am wondering if there is way to perform forEach/map call on method returning a byte and accepting an int as parameter. Example: public class Test { private byte[] byteArray; // example of byte array public byte getByte(int index) { return this.byteArray[index]; } public byte[] getBytes(int... indexes) { return Stream.of(indexes) .map(this::getByte) // should return byte .collect(byte[]::new); // should return byte[] } } As you may guess, the getBytes method