java-stream

E.g: Person result = persons.stream() .filter(x -> { if ("test".equals(x.getName() ) ) { throw new IOException("not possible inside stream y ?"); //any checked exception } //code here }) M looking for reason why it is not being allowed ? Even if method in which code is declared throws IOException Thierry your code is working perfectly, apart from a missing semi colon at the end of the throw new ... line, and from a missing a return statement that may be hidden in // code here . What you can't do is throw a checked exception (which RuntimeException is not) because checked exception are part of

I have a list of tuples, and I want to find the tuples with the largest x value. In the case where there are multiple largest x values, I want to choose one at random. I can't figure out how to implement this random selection functionality. Below is the code I have so far: public void testSelectRandomFromLargestVals() { List<Tuple<Integer, String>> list = new ArrayList<>(); list.add(new Tuple<>(5, "five-1")); list.add(new Tuple<>(2, "two")); list.add(new Tuple<>(3, "three")); list.add(new Tuple<>(5, "five-2")); list.add(new Tuple<>(5, "five-3")); Optional<Tuple<Integer, String>> largestTuple =

I'm trying to translate this (simplified) code to use Java-8 streams: Map<String, String> files = new ConcurrentHashMap<String, String>(); while(((line = reader.readLine()) != null) { if(content != null) files.put("not null"+line, "not null"+line); else files.put("its null"+line, "its null"+line); } reader.close(); Here is what I've tried: files = reader.lines().parallel().collect((content != null)? (Collectors.toConcurrentMap(line->"notnull"+line, line->line+"notnull")) : (Collectors.toConcurrentMap(line->line+"null", line->line+"null"))); But the above gives a "cyclic inference" message for

I have a Map: Map<String, String> utilMap = new HashMap(); utilMap.put("1","1"); utilMap.put("2","2"); utilMap.put("3","3"); utilMap.put("4","4"); I converted it to a String: String utilMapString = utilMap .entrySet() .stream() .map(e -> e.toString()).collect(Collectors.joining(",")); Out put: 1=1,2=2,3=3,4=4,5=5 How to convert utilMapString to Map in Java8? Who can help me with? Split the string by , to get individual map entries. Then split them by = to get the key and the value. Map<String, String> reconstructedUtilMap = Arrays.stream(utilMapString.split(",")) .map(s -> s.split("="))

What is the idiom for performing more than one reduction in a single pass of a stream? Is it just to have one big reducer class, even if this violates SRP if more than one type of reduction computation is required? Stuart Marks Presumably you want to avoid making multiple passes, as the pipeline stages might be expensive. Or you want to avoid collecting the intermediate values in order to run them through multiple collectors, since the cost of storing all the values might be too high. As Brian Goetz noted , Collectors.summarizingInt will collect int values and perform multiple reductions on

For example, given a map like below: { "k1": { "k2": { "k3": { "k4": "v" } } } } and a field list ["k1","k2","k3"] , I need to retrieve the part {"k4": "v"} . Below is my java7-style code: // Ignore the map building code. Map map1 = new HashMap(); Map map2 = new HashMap(); Map map3 = new HashMap(); Map map4 = new HashMap(); map4.put("k4", "v"); map3.put("k3", map4); map2.put("k2", map3); map1.put("k1", map2); Map map = map1; System.out.println(map); //=> {k1={k2={k3={k4=v}}}} // Code to be transformed to java8 style List<String> fields = Arrays.asList("k1", "k2", "k3"); for(String field: