Port of C#'s' 101 LINQ Samples translated into Java 8. (Structure, text and etc copied from mythz Clojure repository)
Execute and display the results of all the examples with:
./gradlew run
For a side-by-side comparison, the original C# source code is displayed above the equivalent Java8 translation.
- The Output shows the console output of running the Java sample.
- Outputs ending with
...illustrates only a partial response is displayed. - The source-code for C# and Clojure utils used are included once under the first section they're used in.
- Unfortunately, Java does not support anonymous record types, so HashMap is used. ObjectDumper substitute for HashMaps in java is located here.
//c#
public void Linq1()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var lowNums =
from n in numbers
where n < 5
select n;
Console.WriteLine("Numbers < 5:");
foreach (var x in lowNums)
{
Console.WriteLine(x);
}
}//java
int[] numbers = {5, 4, 1, 3, 9, 8, 6, 7, 2, 0};
IntStream stream = Arrays.stream(numbers).filter(x -> x < 5);
System.out.println("Numbers < 5:");
stream.forEach(System.out::println);Numbers < 5:
4
1
3
2
0
//c#
public void Linq2()
{
List<Product> products = GetProductList();
var soldOutProducts =
from p in products
where p.UnitsInStock == 0
select p;
Console.WriteLine("Sold out products:");
foreach (var product in soldOutProducts)
{
Console.WriteLine("{0} is sold out!", product.ProductName);
}
}//java
List<Product> products = Objects.getProductList();
Stream<Product> stream = products.stream().filter(x -> x.unitsInStock == 0);
System.out.println("Sold out products:");
stream.map(x -> x.productName).forEach(System.out::println);Sold out products:
Chef Anton's Gumbo Mix is sold out
Alice Mutton is sold out
Thüringer Rostbratwurst is sold out
Gorgonzola Telino is sold out
Perth Pasties is sold out
//c#
public void Linq3()
{
List<Product> products = GetProductList();
var expensiveInStockProducts =
from p in products
where p.UnitsInStock > 0 && p.UnitPrice > 3.00M
select p;
Console.WriteLine("In-stock products that cost more than 3.00:");
foreach (var product in expensiveInStockProducts)
{
Console.WriteLine("{0} is in stock and costs more than 3.00.", product.ProductName);
}
}//java
List<Product> products = Objects.getProductList();
Stream<Product> stream = products.stream().filter(x -> x.unitsInStock > 0 && x.unitPrice > 3.00);
System.out.println("In-stock products that cost more than 3.00:");
stream.map(x -> String.format("%s is in stock and costs more than 3.00.", x.productName))
.forEach(System.out::println);In-stock products that cost more than 3.00:
Chai is in stock and costs more than 3.00
Chang is in stock and costs more than 3.00
Aniseed Syrup is in stock and costs more than 3.00
Chef Anton's Cajun Seasoning is in stock and costs more than 3.00
Grandma's Boysenberry Spread is in stock and costs more than 3.00
//c#
public void Linq4()
{
List<Customer> customers = GetCustomerList();
var waCustomers =
from c in customers
where c.Region == "WA"
select c;
Console.WriteLine("Customers from Washington and their orders:");
foreach (var customer in waCustomers)
{
Console.WriteLine("Customer {0}: {1}", customer.CustomerID, customer.CompanyName);
foreach (var order in customer.Orders)
{
Console.WriteLine(" Order {0}: {1}", order.OrderID, order.OrderDate);
}
}
}//java
System.out.println("Customers from Washington and their orders:");
Stream<Customer> stream = Objects.getCustomerList()
.stream()
.filter(x -> x.region != null && x.region.equals("WA"));
stream.forEach(x -> {
System.out.println(String.format("Customer %s: %s", x.customerID, x.companyName));
for (Order y : x.orders) {
System.out.println(String.format(" Order %s: %s", y.orderID, y.orderDate));
}
});Customer LAZYK: Lazy K Kountry Store
Order 10482: 1997-03-21T00:00
Order 10545: 1997-05-22T00:00
Customer TRAIH: Trail's Head Gourmet Provisioners
Order 10574: 1997-06-19T00:00
Order 10577: 1997-06-23T00:00
Order 10822: 1998-01-08T00:00
...
//c#
public void Linq5()
{
string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
var shortDigits = digits.Where((digit, index) => digit.Length < index);
Console.WriteLine("Short digits:");
foreach (var d in shortDigits)
{
Console.WriteLine("The word {0} is shorter than its value.", d);
}
}//java
String[] digits = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};
System.out.println("Short digits:");
IntStream.range(0, digits.length)
.filter(i -> digits[i].length() < i)
.mapToObj(i -> String.format("The word %s is shorter than its value.", digits[i]))
.forEach(System.out::println);Short digits:
The word five is shorter than its value
The word six is shorter than its value
The word seven is shorter than its value
The word eight is shorter than its value
The word nine is shorter than its value
//c#
public void Linq6()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
var numsPlusOne =
from n in numbers
select n + 1;
Console.WriteLine("Numbers + 1:");
foreach (var i in numsPlusOne)
{
Console.WriteLine(i);
}
}//java
int[] numbers = {5, 4, 1, 3, 9, 8, 6, 7, 2, 0};
System.out.println("Numbers + 1:");
Arrays.stream(numbers).map(x -> x + 1).forEach(System.out::println);Numbers + 1:
6
5
2
4
10
9
7
8
3
1
//c#
public void Linq7()
{
List<Product> products = GetProductList();
var productNames =
from p in products
select p.ProductName;
Console.WriteLine("Product Names:");
foreach (var productName in productNames)
{
Console.WriteLine(productName);
}
}//java
System.out.println("Product Names:");
Objects.getProductList().stream().map(x -> x.productName).forEach(System.out::println);Product Names:
Chai
Chang
Aniseed Syrup
Chef Anton's Cajun Seasoning
Chef Anton's Gumbo Mix
...
//c#
public void Linq8()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
var textNums =
from n in numbers
select strings[n];
Console.WriteLine("Number strings:");
foreach (var s in textNums)
{
Console.WriteLine(s);
}
}//java
int[] numbers = {5, 4, 1, 3, 9, 8, 6, 7, 2, 0};
String[] strings = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};
System.out.println("Number strings:");
Arrays.stream(numbers).mapToObj(x -> strings[x]).forEach(System.out::println);Number strings:
five
four
one
three
nine
eight
six
seven
two
zero
//c#
public void Linq9()
{
string[] words = { "aPPLE", "BlUeBeRrY", "cHeRry" };
var upperLowerWords =
from w in words
select new { Upper = w.ToUpper(), Lower = w.ToLower() };
foreach (var ul in upperLowerWords)
{
Console.WriteLine("Uppercase: {0}, Lowercase: {1}", ul.Upper, ul.Lower);
}
}//java
String[] words = {"aPPLE", "BlUeBeRrY", "cHeRry"};
Arrays.stream(words).map(s -> new HashMap<String, String>() {{
put("Upper", s.toUpperCase());
put("Lower", s.toLowerCase());
}}).forEach(map -> System.out.println(
String.format("Uppercase : %s, Lowercase : %s", map.get("Upper"), map.get("Lower"))));Uppercase: APPLE , Lowercase: apple
Uppercase: BLUEBERRY , Lowercase: blueberry
Uppercase: CHERRY , Lowercase: cherry
//c#
public void Linq10()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
string[] strings = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
var digitOddEvens =
from n in numbers
select new { Digit = strings[n], Even = (n % 2 == 0) };
foreach (var d in digitOddEvens)
{
Console.WriteLine("The digit {0} is {1}.", d.Digit, d.Even ? "even" : "odd");
}
}//java
int[] numbers = {5, 4, 1, 3, 9, 8, 6, 7, 2, 0};
String[] strings = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};
Arrays.stream(numbers).mapToObj(number -> new HashMap<String, Object>() {{
put("Digit", strings[number]);
put("Even", number % 2 == 0);
}}).map(x -> String.format("The digit %s is %s.", x.get("Digit"), x.get("Even").equals(Boolean.FALSE) ? "odd" : "even"))
.forEach(System.out::println);The digit five is odd
The digit four is even
The digit one is odd
The digit three is odd
The digit nine is odd
The digit eight is even
The digit six is even
The digit seven is odd
The digit two is even
The digit zero is even
//c#
public void Linq11()
{
List<Product> products = GetProductList();
var productInfos =
from p in products
select new { p.ProductName, p.Category, Price = p.UnitPrice };
Console.WriteLine("Product Info:");
foreach (var productInfo in productInfos)
{
Console.WriteLine("{0} is in the category {1} and costs {2} per unit.", productInfo.ProductName, productInfo.Category, productInfo.Price);
}
}//java
System.out.println("Product Info:");
Objects.getProductList().stream().map(x -> new HashMap<String, Object>() {{
put("ProductName", x.productName);
put("Category", x.category);
put("Price", x.unitPrice);
}}).map(x -> String.format("%s is in the category %s and costs %f per unit.",
x.get("ProductName"), x.get("Category"), x.get("Price"))).forEach(System.out::println);Product Info:
Chai is in the category Beverages and costs 18.0
Chang is in the category Beverages and costs 19.0
Aniseed Syrup is in the category Condiments and costs 10.0
...
//c#
public void Linq12()
{
int[] numbers = {5, 4, 1, 3, 9, 8, 6, 7, 2, 0};
System.out.println("Number: In-place?");
IntStream.range(0, numbers.length).mapToObj(i -> new HashMap<String, Object>() {{
put("Num", numbers[i]);
put("InPlace", numbers[i] == i);
}}).map(map -> map.get("Num") + ": " + map.get("InPlace")).forEach(System.out::println);
}//java
(defn linq12 []
(let [numbers [5 4 1 3 9 8 6 7 2 0]
nums-in-place
(map-indexed (fn [i num] {:num num, :in-place (= num i)}) numbers)]
(println "Number: In-place?")
(doseq [n nums-in-place]
(println (:num n) ":" (:in-place n)))))Number: In-place?
5 : false
4 : false
1 : false
3 : true
9 : false
8 : false
6 : true
7 : true
2 : false
0 : false
//c#
public void Linq13()
{
int[] numbers = { 5, 4, 1, 3, 9, 8, 6, 7, 2, 0 };
string[] digits = { "zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine" };
var lowNums =
from n in numbers
where n < 5
select digits[n];
Console.WriteLine("Numbers < 5:");
foreach (var num in lowNums)
{
Console.WriteLine(num);
}
}//java
int[] numbers = {5, 4, 1, 3, 9, 8, 6, 7, 2, 0};
String[] digits = {"zero", "one", "two", "three", "four", "five", "six", "seven", "eight", "nine"};
System.out.println("Numbers < 5:");
Arrays.stream(numbers).filter(x -> x < 5).mapToObj(x -> digits[x])
.forEach(System.out::println);Numbers < 5:
four
one
three
two
zero
//c#
public void Linq14()
{
int[] numbersA = { 0, 2, 4, 5, 6, 8, 9 };
int[] numbersB = { 1, 3, 5, 7, 8 };
var pairs =
from a in numbersA
from b in numbersB
where a < b
select new { a, b };
Console.WriteLine("Pairs where a < b:");
foreach (var pair in pairs)
{
Console.WriteLine("{0} is less than {1}", pair.a, pair.b);
}
}//java
int[] numbersA = {0, 2, 4, 5, 6, 8, 9};
int[] numbersB = {1, 3, 5, 7, 8};
System.out.println("Pairs where a < b:");
Arrays.stream(numbersA)
.mapToObj(a -> Arrays.stream(numbersB)
.filter(b -> a < b)
.mapToObj(b -> new HashMap<String, Object>() {{
put("A", a);
put("B", b);
}}))
.flatMap(x -> x)
.map(x -> String.format("%d is less than %d", x.get("A"), x.get("B")))
.forEach(System.out::println);Pairs where a < b:
0 is less than 1
0 is less than 3
0 is less than 5
0 is less than 7
0 is less than 8
2 is less than 3
2 is less than 5
2 is less than 7
2 is less than 8
4 is less than 5
4 is less than 7
4 is less than 8
5 is less than 7
5 is less than 8
6 is less than 7
6 is less than 8
//c#
public void Linq15()
{
List<Customer> customers = GetCustomerList();
var orders =
from c in customers
from o in c.Orders
where o.Total < 500.00M
select new { c.CustomerID, o.OrderID, o.Total };
ObjectDumper.Write(orders);
}//java
List<Customer> customerList = Objects.getCustomerList();
customerList.stream().flatMap(c -> c.orders.stream()
.filter(o -> o.total < 500.0)
.map(o -> new HashMap<String, Object>() {{
put("customerID", c.customerID);
put("orderID", o.orderID);
put("total", o.total);
}})).forEach(ObjectDumper::dump);{:customer-id ALFKI, :order-id 10702, :total 330.00M}
{:customer-id ALFKI, :order-id 10952, :total 471.20M}
{:customer-id ANATR, :order-id 10308, :total 88.80M}
{:customer-id ANATR, :order-id 10625, :total 479.75M}
...
//c#
public void Linq16()
{
List<Customer> customers = GetCustomerList();
var orders =
from c in customers
from o in c.Orders
where o.OrderDate >= new DateTime(1998, 1, 1)
select new { c.CustomerID, o.OrderID, o.OrderDate };
ObjectDumper.Write(orders);
}//java
List<Customer> customerList = Objects.getCustomerList();
customerList.stream().flatMap(c -> c.orders.stream()
.filter(o -> o.orderDate.isAfter(LocalDateTime.of(1998, 1, 1, 0, 0, 0)))
.map(o -> new HashMap<String, Object>() {{
put("customerID", c.customerID);
put("orderID", o.orderID);
put("orderDate", o.orderDate);
}})).forEach(ObjectDumper::dump);{:customer-id ALFKI, :order-id 10835, :order-date #<DateTime 1998-01-15T00:00:00.000-05:00>}
{:customer-id ALFKI, :order-id 10952, :order-date #<DateTime 1998-03-16T00:00:00.000-05:00>}
{:customer-id ALFKI, :order-id 11011, :order-date #<DateTime 1998-04-09T00:00:00.000-04:00>}
{:customer-id ANATR, :order-id 10926, :order-date #<DateTime 1998-03-04T00:00:00.000-05:00>}
{:customer-id ANTON, :order-id 10856, :order-date #<DateTime 1998-01-28T00:00:00.000-05:00>}
...
//c#
public void Linq17()
{
List<Customer> customers = GetCustomerList();
var orders =
from c in customers
from o in c.Orders
where o.Total >= 2000.0M
select new { c.CustomerID, o.OrderID, o.Total };
ObjectDumper.Write(orders);
}//java
List<Customer> customerList = Objects.getCustomerList();
customerList.stream().flatMap(c -> c.orders.stream()
.filter(o -> o.total >= 2000.0)
.map(o -> new HashMap<String, Object>() {{
put("customerID", c.customerID);
put("orderID", o.orderID);
put("total", o.total);
}})).forEach(ObjectDumper::dump);{:customer-id ANTON, :order-id 10573, :total 2082.00M}
{:customer-id AROUT, :order-id 10558, :total 2142.90M}
{:customer-id AROUT, :order-id 10953, :total 4441.25M}
{:customer-id BERGS, :order-id 10384, :total 2222.40M}
{:customer-id BERGS, :order-id 10524, :total 3192.65M}
...
//c#
public void Linq18()
{
List<Customer> customers = GetCustomerList();
DateTime cutoffDate = new DateTime(1997, 1, 1);
var orders =
from c in customers
where c.Region == "WA"
from o in c.Orders
where o.OrderDate >= cutoffDate
select new { c.CustomerID, o.OrderID };
ObjectDumper.Write(orders);
}//java
List<Customer> customerList = Objects.getCustomerList();
LocalDateTime cutoffDate = LocalDateTime.of(1997, 1, 1, 0, 0, 0);
customerList.stream()
.filter(c -> "WA".equals(c.region))
.flatMap(c -> c.orders.stream()
.filter(o -> o.orderDate.isAfter(cutoffDate))
.map(o -> new HashMap<String, Object>() {{
put("customerID", c.customerID);
put("orderID", o.orderID);
}})).forEach(ObjectDumper::dump);{:customer-id LAZYK, :order-id 10482}
{:customer-id LAZYK, :order-id 10545}
{:customer-id TRAIH, :order-id 10574}
{:customer-id TRAIH, :order-id 10577}
{:customer-id TRAIH, :order-id 10822}
{:customer-id WHITC, :order-id 10469}
{:customer-id WHITC, :order-id 10483}
{:customer-id WHITC, :order-id 10504}
{:customer-id WHITC, :order-id 10596}
{:customer-id WHITC, :order-id 10693}
{:customer-id WHITC, :order-id 10696}
{:customer-id WHITC, :order-id 10723}
{:customer-id WHITC, :order-id 10740}
{:customer-id WHITC, :order-id 10861}
{:customer-id WHITC, :order-id 10904}
{:customer-id WHITC, :order-id 11032}
{:customer-id WHITC, :order-id 11066}
//c#
public void Linq19()
{
List<Customer> customers = GetCustomerList();
var customerOrders =
customers.SelectMany(
(cust, custIndex) =>
cust.Orders.Select(o => "Customer #" + (custIndex + 1) +
" has an order with OrderID " + o.OrderID));
ObjectDumper.Write(customerOrders);
}//java
List<Customer> customerList = Objects.getCustomerList();
IntStream.range(0, customerList.size())
.mapToObj(i -> customerList.get(i).orders.stream().map(o ->
"Customer #" + (i + 1) + " has an order with OrderID " + o.orderID))
.flatMap(x -> x).forEach(System.out::println);Customer #1 has an order with OrderID 10643
Customer #1 has an order with OrderID 10692
Customer #1 has an order with OrderID 10702
Customer #1 has an order with OrderID 10835
Customer #1 has an order with OrderID 10952
Customer #1 has an order with OrderID 11011
Customer #2 has an order with OrderID 10308
Customer #2 has an order with OrderID 10625
Customer #2 has an order with OrderID 10759
Customer #2 has an order with OrderID 10926
...