java-8

问题 I have a requirement to log/sysout the filtered values in Java Streams. I am able to log/sysout the non-filtered value using peek() method. However, can someone please let me know how to log filtered values? For example, let's say I have a list of Person objects like this: List<Person> persons = Arrays.asList(new Person("John"), new Person("Paul")); I want to filter out those persons who are not "John" as follows: persons.stream().filter(p -> !"John".equals(p.getName())).collect(Collectors

问题 Suppose I have a map of given name, surname pairs and I want to find the given name of the first entry in that map that has the surname matching a certain value. How would we do this in a java 8 fashion. In my test case example below I put two ways that would do it. However the first one (looking for the given name of the first person with a surname of "Donkey") will throw java.util.NoSuchElementException: No value present so it is not safe. The second one works but it is not only harder to

问题 Closed. This question is not reproducible or was caused by typos. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 11 days ago . Improve this question I have a class like class Employee String id String name I want to filter out the list of employees based on the list of deptId which is an integer list Employee emp1 = new Employee("1","Ally"); Employee emp2 = new Employee("2","Billy"); ArrayList<Employee>

问题 Closed. This question is not reproducible or was caused by typos. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 11 days ago . Improve this question I have a class like class Employee String id String name I want to filter out the list of employees based on the list of deptId which is an integer list Employee emp1 = new Employee("1","Ally"); Employee emp2 = new Employee("2","Billy"); ArrayList<Employee>

问题 Closed. This question is not reproducible or was caused by typos. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 11 days ago . Improve this question I have a class like class Employee String id String name I want to filter out the list of employees based on the list of deptId which is an integer list Employee emp1 = new Employee("1","Ally"); Employee emp2 = new Employee("2","Billy"); ArrayList<Employee>

问题 Closed. This question is not reproducible or was caused by typos. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 11 days ago . Improve this question I have a class like class Employee String id String name I want to filter out the list of employees based on the list of deptId which is an integer list Employee emp1 = new Employee("1","Ally"); Employee emp2 = new Employee("2","Billy"); ArrayList<Employee>

问题 Closed. This question is not reproducible or was caused by typos. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 11 days ago . Improve this question I have a class like class Employee String id String name I want to filter out the list of employees based on the list of deptId which is an integer list Employee emp1 = new Employee("1","Ally"); Employee emp2 = new Employee("2","Billy"); ArrayList<Employee>

问题 Closed. This question is not reproducible or was caused by typos. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 11 days ago . Improve this question I have a class like class Employee String id String name I want to filter out the list of employees based on the list of deptId which is an integer list Employee emp1 = new Employee("1","Ally"); Employee emp2 = new Employee("2","Billy"); ArrayList<Employee>

问题 This question already has answers here : Find maximum, minimum, sum and average of a list in Java 8 (3 answers) Closed last year . I have List of Integres and want get min, max and avg from list to Map. Below is my code, List<Integer> numbers = Arrays.asList(-2, 1, 2, 3, 5, 6, 7, 8, 9, 10, 100); int min = numbers.stream().mapToInt(n -> n).min().getAsInt(); int max = numbers.stream().mapToInt(n->n).max().getAsInt(); double avg = numbers.stream().mapToInt(n->n).average().getAsDouble(); Map

问题 I have three Optional> which have to be combined and returned. I tried to use Optional.map() and flatmap() but was not successful. public Optional<List<Entiy>> getRecords() { Optional<List<Entiy>> entity1 = repo.findAllByStatus("1"); Optional<List<Entiy>> entity2 = repo.findAllByStatus("2"); Optional<List<Entiy>> entity3 = repo.findAllByStatus("3"); //Need to return a concatenation of entity1, 2 and 3 } Any thoughts on how to do is efficiently? 回答1: Something like : return Optional.of(Stream