java-stream

问题 I have the Person class: import java.util.*; public class Person { private String name; Map<String,Integer> Skills=new HashMap<>(); // skill name(String) and level(int) public String getName(){ return this.name; } public Map<String,Integer> getSkills(){ return this.Skills; } } And the App class: import java.util.*; import java.util.Map.Entry; import static java.util.stream.Collectors.*; import static java.util.Comparator.*; public class App { private List<Person> people=new ArrayList<>(); //

问题 I have a method that has to remove any element listed in a (small) Set<K> keysToRemove from some (potentially large) Map<K,V> from . But removeAll() doesn't do, as I need to return all keys that were actually removed, since the map might or might not contain keys that require removal. Old-school code is straight forward: public Set<K> removeEntries(Map<K, V> from) { Set<K> fromKeys = from.keySet(); Set<K> removedKeys = new HashSet<>(); for (K keyToRemove : keysToRemove) { if (fromKeys

问题 I have a method that has to remove any element listed in a (small) Set<K> keysToRemove from some (potentially large) Map<K,V> from . But removeAll() doesn't do, as I need to return all keys that were actually removed, since the map might or might not contain keys that require removal. Old-school code is straight forward: public Set<K> removeEntries(Map<K, V> from) { Set<K> fromKeys = from.keySet(); Set<K> removedKeys = new HashSet<>(); for (K keyToRemove : keysToRemove) { if (fromKeys

问题 I have a method that has to remove any element listed in a (small) Set<K> keysToRemove from some (potentially large) Map<K,V> from . But removeAll() doesn't do, as I need to return all keys that were actually removed, since the map might or might not contain keys that require removal. Old-school code is straight forward: public Set<K> removeEntries(Map<K, V> from) { Set<K> fromKeys = from.keySet(); Set<K> removedKeys = new HashSet<>(); for (K keyToRemove : keysToRemove) { if (fromKeys

问题 I have a method that has to remove any element listed in a (small) Set<K> keysToRemove from some (potentially large) Map<K,V> from . But removeAll() doesn't do, as I need to return all keys that were actually removed, since the map might or might not contain keys that require removal. Old-school code is straight forward: public Set<K> removeEntries(Map<K, V> from) { Set<K> fromKeys = from.keySet(); Set<K> removedKeys = new HashSet<>(); for (K keyToRemove : keysToRemove) { if (fromKeys

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 needs debugging details. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 days ago . Improve this question I'm trying to sort list of maps based on specific key lets say "tax" with int values in all the maps. However other keys like "id" and "price" have string and double type values respectively as shown below. List<Map<String, Object>> taxes = Arrays.asList(Map.of("id", "3", "tax",

问题 Closed. This question needs debugging details. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 days ago . Improve this question I'm trying to sort list of maps based on specific key lets say "tax" with int values in all the maps. However other keys like "id" and "price" have string and double type values respectively as shown below. List<Map<String, Object>> taxes = Arrays.asList(Map.of("id", "3", "tax",

问题 Closed. This question needs debugging details. It is not currently accepting answers. Want to improve this question? Update the question so it's on-topic for Stack Overflow. Closed 5 days ago . Improve this question I'm trying to sort list of maps based on specific key lets say "tax" with int values in all the maps. However other keys like "id" and "price" have string and double type values respectively as shown below. List<Map<String, Object>> taxes = Arrays.asList(Map.of("id", "3", "tax",