I have the following list of strings
List<String> product_a= Arrays.asList("Product A", "Category A", "Price");
List<String> product_b= Arrays.asList("Product A", "Category A", "Price");
List<String> product_c= Arrays.asList("Product B", "Category B", "Price");
List<String> product_d = Arrays.asList("Product C", "Category C", "Price");
Then, I put them in another list
List<List<String>> products = new ArrayList<>();
products.add(product_a);
products.add(product_b);
products.add(product_c);
products.add(product_d);
Using streams, Collectors.groupingBy, Collectors.counting, how can I get the following output? is it possible?
Product A - 2
Product B - 1
Product C - 1
In advance, thank you for your help.
You mean :
Map<String, Long> group = products.stream()
.collect(Collectors.groupingBy(c -> c.get(0), Collectors.counting()));
group.entrySet().forEach(c -> System.out.println(c.getKey() + " - " + c.getValue()));
Outputs
Product A - 2
Product B - 1
Product C - 1
But I would like to create a class which hold this three information product
category
price
instead of using List for each item.
class Product{
private String productName;
private String category;
private BigDecimal price;
//constructors getters setters
}
Then fill your products in an List of Product like so :
List<Product> products = new ArrayList<>();
products.add(new Product("Product A", "Category A", new BigDecimal("123")));
products.add(new Product("Product A", "Category A", new BigDecimal("456")));
products.add(new Product("Product B", "Category B", new BigDecimal("696")));
products.add(new Product("Product C", "Category C", new BigDecimal("66")));
Then you grouping can be :
Map<String, Long> group = products.stream()
.collect(Collectors.groupingBy(Product::getProductName, Collectors.counting()));
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