A little example, I had to develop as a teaching use case, of how to take a map with Integer keys and values with a List as value and find a specific value in any List in the whole map using Java Streams.
boolean b1 returns true because the element exists
boolean b2 is the response to an element that doesn’t exist
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package com.company; import java.util.*; import java.util.stream.Collectors; public class Main { public static void main(String[] args) { Map<Integer, List<String>> hm = new HashMap<>(); hm.put(1, getRandomListValues(1)); hm.put(2, getRandomListValues(2)); hm.put(3, getRandomListValues(3)); hm.put(4, getRandomListValues(4)); hm.put(5, getRandomListValues(5)); boolean b1 = hm.values().stream().flatMap(l -> l.stream()).anyMatch(i -> i.equals("3-2")); boolean b2 = hm.values().stream().flatMap(l -> l.stream()).anyMatch(i -> i.equals("33-2")); System.out.println(b1); System.out.println(b2); } private static List<String> getRandomListValues(int v) { List<String> l = new ArrayList<>(); for(int i = 0; i < 10; i++) { l.add(v + "-" + i); } return l; } } |
