TreeMap counting

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import java.util.List; import java.util.Map; import java.util.TreeMap; import java.util.Random; import java.util.stream.Stream; import java.util.stream.IntStream; class Main { public static void main(String[] args) { // Data generation Random rand = new Random(); List<String> productNames = List.of("Mouse", "Keyboard", "Battery", "Laptop", "Pad Mouse", "Ethernet Cable") .stream() .flatMap(product -> Stream.generate(() -> product).limit(rand.nextInt(20 - 1) + 1)) .toList(); Map<String, Integer> productsByCategories = new TreeMap<>(); // Categorization for (String productName: productNames) { if (productsByCategories.containsKey(productName)) { var count = productsByCategories.get(productName) + 1; productsByCategories.put(productName, count); } else { productsByCategories.put(productName, 1); } } // Print output System.out.println("Product names: " + productNames); for (Map.Entry<String, Integer> productByCategory : productsByCategories.entrySet()) { System.out.println("Product: " + productByCategory.getKey() + " - " + productByCategory.getValue()); } } }
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