Differences

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--- programming:java:java8 [2017/06/14 13:49] – ↷ Page moved from java:java8 to programming:java:java8 skipidar
+++ programming:java:java8 [2023/11/01 07:31] (current) – ↷ Page moved from camunda:programming:java:java8 to programming:java:java8 skipidar
@@ Line 301: / Line 301: @@
-THe floowing code would produce the floowing output:
+THe following code would produce the floowing output:
 **code**
-<code>
+<sxh java>
-dishes.stream().filter(a -> {System.out.println(a.name); return true;}).distinct().map(a -> {System.out.println(a.type); return a.name;});
+        dishes.stream().filter(a -> {
-</code>
+            System.out.println(a.name);
+            return true;
+        }).distinct().map(a -> {
+            System.out.println(a.type);
+            return a.name;
+        });
+</sxh>
 **output**
@@ Line 319: / Line 325: @@
-This means that steps during parallel execution - methods which can block the parallel execution should not be executed inside the Stream-pipeline.
+This means that steps during parallel execution - methods that can block the parallel execution should not be executed inside the Stream-pipeline.
@@ Line 372: / Line 378: @@
 | reducing | The type produced by the reduction operation  | Reduce the stream to a single value starting from an initial value used as accumulator and iteratively combining it with each item of the stream using a BinaryOperator.  | <code> int totalCalories = menuStream.collect(reducing(0, Dish::getCalories, Integer::sum));  </code> |
 | collectingAndThen  | The type returned by the transforming function  |   | <code> int howManyDishes = menuStream.collect(collectingAndThen(toList(), List::size));   </code> |
-| groupingBy | Map<K, List<T>> | Maps the stream to groups (as hashmap keys)  | <code> Map<Dish.Type, List<Dish>> dishesByType = menuStream.collect(groupingBy(Dish::getType)); </code> |
+| groupingBy | Map<K, List<T>> | Maps the stream to groups (as hashmap keys)  | <sxh java> Map<Dish.Type, List<Dish>> dishesByType = menuStream.collect(groupingBy(Dish::getType)); </sxh> |
 | partitioningBy | Map<Boolean, List<T>> |  | <code> Map<Boolean, List<Dish>> vegetarianDishes =menuStream.collect(partitioningBy(Dish::isVegetarian)); </code> |
@@ Line 558: / Line 564: @@
 to execute some code when the future has completed the computation.
-<sxh>
+<sxh java>
 CompletableFuture<Integer> c = null;
 CompletableFuture<String> c2 = null;
@@ Line 958: / Line 964: @@
 </sxh>
+===== Interfaces relevant for Lambdas =====
+If you would like to create a method accepting a lamda use the Argument, typed with one of those methods:
+**java.util.function.IntBinaryOperator.**
+Examples:
+<sxh java>
+Consumer<Double> c = aDouble -> System.out.println(aDouble);  // no output
+Function<Double, String> f = aDouble -> String.valueOf(f);  // function returns what you define
+DoubleFunction<String> d = doubleValue -> String.valueOf(doubleValue); // same as previous
+IntBinaryOperator plusOperation = (a, b) -> a + b; // operator on two int numbers a and b
+LongPredicate l = longValue -> longValue < 0l; // boolean function
+</sxh>
+===== Terminal Methods =====
+== findAny / findFirst ==
+<sxh java>
+            List<Integer> list = List.of(1, 2, 3, 4, 9, 8, 7, 6, 1, 2, 3);
+            // gives maybe 7, 8 or 9, cause findAny doesnt respect order
+            int res = list
+                    .stream()
+                    .parallel()
+                    .filter(integer -> integer > 6)
+                    .findAny()
+                    .orElseThrow();
+            assertThat(res, anyOf(is(7), is(8), is(9)));
+            // gives 9, cause its the first in the row match to filter
+            int res2 = list
+                    .stream()
+                    .parallel()
+                    .filter(integer -> integer > 6)
+                    .findFirst()
+                    .orElseThrow();
+            assertThat(res, is(9));
+</sxh>
+== reduce ==
+<sxh java>
+        // cruel method to concat numbers, just to demonstrate reduce
+        List<Integer> list = List.of(1, 2, 3, 4, 9, 8, 7, 6, 1, 2);
+        Integer res = list
+                .stream()
+                .mapToInt(value -> value)
+                .reduce(0,
+                        (integer, integer2) -> {
+                            return Integer.parseInt(String.format("%s%s", integer, integer2));
+                        }
+                );
+        System.out.println(res); // 1234987612
+        // better way would be with java8
+        String res2 = list
+                .stream()
+                .map(String::valueOf)
+                .collect(Collectors.joining());
+        System.out.println(res2); // 1234987612
+</sxh>