Grouping by collector java (#11001)

* Initial Commit - Ports and Adapters

* Restructured code to implement input and outbou ports and adapters

* Added tests for groupingBy Collector

* Revert "Initial Commit - Ports and Adapters"

This reverts commit 55152dea

* Added tests for groupingBy Collector

* reverting

* corrected typo

* used BDD naming strategy for tests

* Added a test for groupingByConcurrent

* added new module and package

* added core-java-streams-4 module in main pom.xml

* updated pom.xml and changed artifactId

* removed gitignore and README.md
Converted spaces to tabs and reformatted code

* removed gitignore and README.md

* used baeldung formatter

core-java-modules/core-java-streams-4/README.md

@@ -1,6 +0,0 @@
-## Core Java streams
-
-This module contains articles about the Stream API in Java.
-
-### Relevant Articles: 
-- [Count Occurrences using Java groupingBy Collector](https://baeldung.com/count-occurrences-with-java-groupingby-collector)

core-java-modules/core-java-streams-4/src/test/java/com/baeldung/streamcollectors/StreamGroupingByCollectorUnitTest.java

@@ -10,90 +10,75 @@ import java.util.stream.Collectors;
 import org.junit.Assert;
 import org.junit.Test;
 
-public class StreamGroupingByCollectorUnitTest
+public class StreamGroupingByCollectorUnitTest {
-{
+    @Test
-        static class Employee {
+    public void givenListOfStrings_whenGroupingEqualStrings_thenUseCollectorsGroupingByToGroupEqualStringsAndCountOfOccurrences() {
 
-                Integer employeeId;
+        List<String> list = new ArrayList<>(Arrays.asList("Foo", "Bar", "Bar", "Foo", "Bar"));
-                String employeeName;
-                Integer departmentId;
 
-                Employee(Integer employeeId, String employeeName, Integer departmentId) {
+        Map<String, Long> result = list.stream().collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
-                        this.employeeId = employeeId;
+        Assert.assertEquals(new Long(2), result.get("Foo"));
-                        this.employeeName = employeeName;
+        Assert.assertEquals(new Long(3), result.get("Bar"));
-                        this.departmentId = departmentId;
-                }
 
-                public Integer getEmployeeId() {
+    }
-                        return employeeId;
-                }
 
-                public void setEmployeeId(Integer employeeId) {
+    @Test
-                        this.employeeId = employeeId;
+    public void givenListOfStrings_whenGroupingEqualLengthStrings_thenUseCollectorsGroupingByConcurrentToGroupEqualLengthStringsAndCountOfOccurrences() {
-                }
 
-                public String getEmployeeName() {
+        List<String> list = new ArrayList<>(Arrays.asList("Adam", "Bill", "Jack", "Joe", "Ian"));
-                        return employeeName;
-                }
 
-                public void setEmployeeName(String employeeName) {
+        Map<Integer, Long> result = list.stream().collect(Collectors.groupingByConcurrent(String::length, Collectors.counting()));
-                        this.employeeName = employeeName;
+        Assert.assertEquals(new Long(2), result.get(3));
-                }
+        Assert.assertEquals(new Long(3), result.get(4));
 
-                public Integer getDepartmentId() {
+    }
-                        return departmentId;
-                }
 
-                public void setDepartmentId(Integer departmentId) {
+    @Test
-                        this.departmentId = departmentId;
+    public void givenListOfEmployees_whenGroupingDepartmentId_thenUseCollectorsGroupingByDepartmentIdAndCountNumberOfEmployeesWithinEveryDepartment() {
-                }
+
+        List<Employee> list = new ArrayList<>(Arrays.asList(new Employee(1, "Joe", 1), new Employee(2, "Josh", 1), new Employee(3, "Jamie", 2), new Employee(4, "Jim", 2), new Employee(5, "Jack", 2)));
+
+        Map<Integer, Long> result = list.stream().collect(Collectors.groupingBy(Employee::getDepartmentId, Collectors.counting()));
+        Assert.assertEquals(new Long(2), result.get(1));
+        Assert.assertEquals(new Long(3), result.get(2));
+
+    }
+
+    static class Employee {
+
+        Integer employeeId;
+        String employeeName;
+        Integer departmentId;
+
+        Employee(Integer employeeId, String employeeName, Integer departmentId) {
+            this.employeeId = employeeId;
+            this.employeeName = employeeName;
+            this.departmentId = departmentId;
         }
 
-        @Test
+        public Integer getEmployeeId() {
-        public void
+            return employeeId;
-        givenListOfStrings_whenGroupingEqualStrings_thenUseCollectorsGroupingByToGroupEqualStringsAndCountOfOccurrences()  {
-                List<String> list = new ArrayList<>(
-                    Arrays.asList("Foo", "Bar", "Bar", "Foo", "Bar")
-                );
-
-                Map<String, Long> result = list.stream().collect(Collectors.groupingBy(Function.identity(), Collectors.counting()));
-                Assert.assertEquals(new Long(2), result.get("Foo"));
-                Assert.assertEquals(new Long(3), result.get("Bar"));
-
         }
 
-        @Test
+        public void setEmployeeId(Integer employeeId) {
-        public void
+            this.employeeId = employeeId;
-        givenListOfStrings_whenGroupingEqualLengthStrings_thenUseCollectorsGroupingByConcurrentToGroupEqualLengthStringsAndCountOfOccurrences()  {
-
-                List<String> list = new ArrayList<>(
-                    Arrays.asList("Adam", "Bill", "Jack", "Joe", "Ian")
-                );
-
-                Map<Integer, Long> result = list.stream()
-                    .collect(Collectors.groupingByConcurrent(String::length, Collectors.counting()));
-                Assert.assertEquals(new Long(2), result.get(3));
-                Assert.assertEquals(new Long(3), result.get(4));
-
         }
 
-
+        public String getEmployeeName() {
-        @Test
+            return employeeName;
-        public void
-        givenListOfEmployees_whenGroupingDepartmentId_thenUseCollectorsGroupingByDepartmentIdAndCountNumberOfEmployeesWithinEveryDepartment()  {
-
-                List<Employee> list = new ArrayList<>(
-                    Arrays.asList(new Employee(1, "Joe", 1),
-                                  new Employee(2, "Josh", 1),
-                                  new Employee(3, "Jamie", 2),
-                                  new Employee(4, "Jim", 2),
-                                  new Employee(5, "Jack", 2))
-                );
-
-                Map<Integer, Long> result = list.stream() .collect(Collectors.groupingBy(Employee::getDepartmentId, Collectors.counting()));
-                Assert.assertEquals(new Long(2), result.get(1));
-                Assert.assertEquals(new Long(3), result.get(2));
-
         }
 
+        public void setEmployeeName(String employeeName) {
+            this.employeeName = employeeName;
+        }
+
+        public Integer getDepartmentId() {
+            return departmentId;
+        }
+
+        public void setDepartmentId(Integer departmentId) {
+            this.departmentId = departmentId;
+        }
+    }
+
 }

core-java-modules/core-java-streams-4/src/test/resources/.gitignore

@@ -1,13 +0,0 @@
-*.class
-
-#folders#
-/target
-/neoDb*
-/data
-/src/main/webapp/WEB-INF/classes
-*/META-INF/*
-
-# Packaged files #
-*.jar
-*.war
-*.ear