merge from upstream

2018-01-07 14:29:47 +01:00
parent f4903c6118 477e8cfef4
commit b60e5ac763
317 changed files with 6587 additions and 1393 deletions
@@ -3,7 +3,8 @@ language: java
 before_install: 
  - echo "MAVEN_OPTS='-Xmx2048M -Xss128M -XX:+CMSClassUnloadingEnabled -XX:+UseG1GC -XX:-UseGCOverheadLimit'" > ~/.mavenrc

-install: travis_wait 60 mvn -q test -fae
+install: skip
+script: travis_wait 60 mvn -q test -fae

 sudo: required

@@ -39,6 +39,12 @@
            <artifactId>jgrapht-core</artifactId>
            <version>1.0.1</version>
        </dependency>
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>3.9.0</version>
+            <scope>test</scope>
+        </dependency>
    </dependencies>

    <build>
@@ -0,0 +1,111 @@
+package com.baeldung.algorithms.kthlargest;
+
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.stream.IntStream;
+
+public class FindKthLargest {
+
+    public int findKthLargestBySorting(Integer[] arr, int k) {
+        Arrays.sort(arr);
+        int targetIndex = arr.length - k;
+        return arr[targetIndex];
+    }
+
+    public int findKthLargestBySortingDesc(Integer[] arr, int k) {
+        Arrays.sort(arr, Collections.reverseOrder());
+        return arr[k - 1];
+    }
+
+    public int findKthElementByQuickSelect(Integer[] arr, int left, int right, int k) {
+        if (k >= 0 && k <= right - left + 1) {
+            int pos = partition(arr, left, right);
+            if (pos - left == k) {
+                return arr[pos];
+            }
+            if (pos - left > k) {
+                return findKthElementByQuickSelect(arr, left, pos - 1, k);
+            }
+            return findKthElementByQuickSelect(arr, pos + 1, right, k - pos + left - 1);
+        }
+        return 0;
+    }
+
+    public int findKthElementByQuickSelectWithIterativePartition(Integer[] arr, int left, int right, int k) {
+        if (k >= 0 && k <= right - left + 1) {
+            int pos = partitionIterative(arr, left, right);
+            if (pos - left == k) {
+                return arr[pos];
+            }
+            if (pos - left > k) {
+                return findKthElementByQuickSelectWithIterativePartition(arr, left, pos - 1, k);
+            }
+            return findKthElementByQuickSelectWithIterativePartition(arr, pos + 1, right, k - pos + left - 1);
+        }
+        return 0;
+    }
+
+    private int partition(Integer[] arr, int left, int right) {
+        int pivot = arr[right];
+        Integer[] leftArr;
+        Integer[] rightArr;
+
+        leftArr = IntStream.range(left, right)
+            .filter(i -> arr[i] < pivot)
+            .map(i -> arr[i])
+            .boxed()
+            .toArray(Integer[]::new);
+
+        rightArr = IntStream.range(left, right)
+            .filter(i -> arr[i] > pivot)
+            .map(i -> arr[i])
+            .boxed()
+            .toArray(Integer[]::new);
+
+        int leftArraySize = leftArr.length;
+        System.arraycopy(leftArr, 0, arr, left, leftArraySize);
+        arr[leftArraySize + left] = pivot;
+        System.arraycopy(rightArr, 0, arr, left + leftArraySize + 1, rightArr.length);
+
+        return left + leftArraySize;
+    }
+
+    private int partitionIterative(Integer[] arr, int left, int right) {
+        int pivot = arr[right], i = left;
+        for (int j = left; j <= right - 1; j++) {
+            if (arr[j] <= pivot) {
+                swap(arr, i, j);
+                i++;
+            }
+        }
+        swap(arr, i, right);
+        return i;
+    }
+
+    public int findKthElementByRandomizedQuickSelect(Integer[] arr, int left, int right, int k) {
+        if (k >= 0 && k <= right - left + 1) {
+            int pos = randomPartition(arr, left, right);
+            if (pos - left == k) {
+                return arr[pos];
+            }
+            if (pos - left > k) {
+                return findKthElementByRandomizedQuickSelect(arr, left, pos - 1, k);
+            }
+            return findKthElementByRandomizedQuickSelect(arr, pos + 1, right, k - pos + left - 1);
+        }
+        return 0;
+    }
+
+    private int randomPartition(Integer arr[], int left, int right) {
+        int n = right - left + 1;
+        int pivot = (int) (Math.random()) % n;
+        swap(arr, left + pivot, right);
+        return partition(arr, left, right);
+    }
+
+    private void swap(Integer[] arr, int n1, int n2) {
+        int temp = arr[n2];
+        arr[n2] = arr[n1];
+        arr[n1] = temp;
+    }
+}
@@ -0,0 +1,57 @@
+package com.baeldung.algorithms.kthlargest;
+
+import static org.assertj.core.api.Assertions.*;
+
+import org.junit.Before;
+import org.junit.Test;
+
+public class FindKthLargestUnitTest {
+
+    private FindKthLargest findKthLargest;
+    private Integer[] arr = { 3, 7, 1, 2, 8, 10, 4, 5, 6, 9 };
+
+    @Before
+    public void setup() {
+        findKthLargest = new FindKthLargest();
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthLargestBySorting_thenGetResult() {
+        int k = 3;
+        assertThat(findKthLargest.findKthLargestBySorting(arr, k)).isEqualTo(8);
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthLargestBySortingDesc_thenGetResult() {
+        int k = 3;
+        assertThat(findKthLargest.findKthLargestBySortingDesc(arr, k)).isEqualTo(8);
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthLargestByQuickSelect_thenGetResult() {
+        int k = 3;
+        int kthLargest = arr.length - k;
+        assertThat(findKthLargest.findKthElementByQuickSelect(arr, 0, arr.length - 1, kthLargest)).isEqualTo(8);
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthElementByQuickSelectIterative_thenGetResult() {
+        int k = 3;
+        int kthLargest = arr.length - k;
+        assertThat(findKthLargest.findKthElementByQuickSelectWithIterativePartition(arr, 0, arr.length - 1, kthLargest)).isEqualTo(8);
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthSmallestByQuickSelect_thenGetResult() {
+        int k = 3;
+        assertThat(findKthLargest.findKthElementByQuickSelect(arr, 0, arr.length - 1, k - 1)).isEqualTo(3);
+    }
+
+    @Test
+    public void givenIntArray_whenFindKthLargestByRandomizedQuickSelect_thenGetResult() {
+        int k = 3;
+        int kthLargest = arr.length - k;
+        assertThat(findKthLargest.findKthElementByRandomizedQuickSelect(arr, 0, arr.length - 1, kthLargest)).isEqualTo(8);
+    }
+
+}
@@ -9,7 +9,7 @@
  <url>http://maven.apache.org</url>
  
  <properties>
-        <maven-compiler-plugin.version>3.6.0</maven-compiler-plugin.version>	
+        <maven-compiler-plugin.version>3.7.0</maven-compiler-plugin.version>	
    </properties>
 	
  <dependencies>
@@ -26,8 +26,8 @@
 				  <artifactId>maven-compiler-plugin</artifactId>
 				  <version>3.7.0</version>
 				  <configuration>
-					<source>1.6</source>
-					<target>1.6</target>
+					<source>1.8</source>
+					<target>1.8</target>
 				  </configuration>
 				</plugin>
 				<plugin>
@@ -15,7 +15,7 @@

    <properties>
        <auto-service.version>1.0-rc2</auto-service.version>
-        <maven-compiler-plugin.version>3.6.0</maven-compiler-plugin.version>
+        <maven-compiler-plugin.version>3.7.0</maven-compiler-plugin.version>
    </properties>

    <dependencies>
@@ -65,7 +65,7 @@
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.6.2</version>
+                <version>3.7.0</version>
                <configuration>
                    <source>1.8</source>
                    <target>1.8</target>
@@ -12,7 +12,7 @@

 	<properties>
 		<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
-		<maven-compiler-plugin.version>3.6.0</maven-compiler-plugin.version>
+		<maven-compiler-plugin.version>3.7.0</maven-compiler-plugin.version>
 		<maven-surefire-plugin.version>2.19.1</maven-surefire-plugin.version>
 		<camel.version>2.19.1</camel.version>
 	    <spring-boot-starter.version>1.5.4.RELEASE</spring-boot-starter.version>
@@ -52,7 +52,11 @@
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
-                <version>3.3</version>
+                <version>3.7.0</version>
+                <configuration>
+                    <source>1.8</source>
+                    <target>1.8</target>
+                </configuration>
            </plugin>
        </plugins>
        <finalName>cas</finalName>
@@ -33,3 +33,4 @@
 - [Display All Time Zones With GMT And UTC in Java](http://www.baeldung.com/java-time-zones)
 - [Copy a File with Java](http://www.baeldung.com/java-copy-file)
 - [Generating Prime Numbers in Java](http://www.baeldung.com/java-generate-prime-numbers)
+- [Static and Default Methods in Interfaces in Java](http://www.baeldung.com/java-static-default-methods)
@@ -2,7 +2,6 @@ package com.baeldung.datetime;

 import java.time.Duration;
 import java.time.LocalTime;
-import java.time.Period;

 public class UseDuration {

@@ -0,0 +1,18 @@
+package com.baeldung.defaultstaticinterfacemethods.application;
+
+import com.baeldung.defaultstaticinterfacemethods.model.Car;
+import com.baeldung.defaultstaticinterfacemethods.model.Vehicle;
+
+public class Application {
+
+    public static void main(String[] args) {
+
+        Vehicle car = new Car("BMW");
+        System.out.println(car.getBrand());
+        System.out.println(car.speedUp());
+        System.out.println(car.slowDown());
+        System.out.println(car.turnAlarmOn());
+        System.out.println(car.turnAlarmOff());
+        System.out.println(Vehicle.getHorsePower(2500, 480));
+    }
+}
@@ -0,0 +1,12 @@
+package com.baeldung.defaultstaticinterfacemethods.model;
+
+public interface Alarm {
+
+    default String turnAlarmOn() {
+        return "Turning the alarm on.";
+    }
+
+    default String turnAlarmOff() {
+        return "Turning the alarm off.";
+    }
+}
@@ -0,0 +1,25 @@
+package com.baeldung.defaultstaticinterfacemethods.model;
+
+public class Car implements Vehicle {
+
+    private final String brand;
+
+    public Car(String brand) {
+        this.brand = brand;
+    }
+
+    @Override
+    public String getBrand() {
+        return brand;
+    }
+
+    @Override
+    public String speedUp() {
+        return "The car is speeding up.";
+    }
+
+    @Override
+    public String slowDown() {
+        return "The car is slowing down.";
+    }
+}
@@ -0,0 +1,25 @@
+package com.baeldung.defaultstaticinterfacemethods.model;
+
+public class Motorbike implements Vehicle {
+
+    private final String brand;
+
+    public Motorbike(String brand) {
+        this.brand = brand;
+    }
+
+    @Override
+    public String getBrand() {
+        return brand;
+    }
+
+    @Override
+    public String speedUp() {
+        return "The motorbike is speeding up.";
+    }
+
+    @Override
+    public String slowDown() {
+        return "The motorbike is slowing down.";
+    }
+}
@@ -0,0 +1,35 @@
+package com.baeldung.defaultstaticinterfacemethods.model;
+
+public class MultiAlarmCar implements Vehicle, Alarm {
+
+    private final String brand;
+
+    public MultiAlarmCar(String brand) {
+        this.brand = brand;
+    }
+
+    @Override
+    public String getBrand() {
+        return brand;
+    }
+
+    @Override
+    public String speedUp() {
+        return "The motorbike is speeding up.";
+    }
+
+    @Override
+    public String slowDown() {
+        return "The mootorbike is slowing down.";
+    }
+
+    @Override
+    public String turnAlarmOn() {
+        return Vehicle.super.turnAlarmOn() + " " + Alarm.super.turnAlarmOn();
+    }
+
+    @Override
+    public String turnAlarmOff() {
+        return Vehicle.super.turnAlarmOff() + " " + Alarm.super.turnAlarmOff();
+    }
+}
@@ -0,0 +1,22 @@
+package com.baeldung.defaultstaticinterfacemethods.model;
+
+public interface Vehicle {
+
+    String getBrand();
+
+    String speedUp();
+
+    String slowDown();
+
+    default String turnAlarmOn() {
+        return "Turning the vehice alarm on.";
+    }
+
+    default String turnAlarmOff() {
+        return "Turning the vehicle alarm off.";
+    }
+
+    static int getHorsePower(int rpm, int torque) {
+        return (rpm * torque) / 5252;
+    }
+}
@@ -0,0 +1,80 @@
+package com.baeldung.iterators;
+
+import java.util.ArrayList;
+import java.util.Iterator;
+import java.util.concurrent.ConcurrentHashMap;
+
+/**
+ * Source code https://github.com/eugenp/tutorials
+ *
+ * @author Santosh Thakur
+ */
+
+public class Iterators {
+
+    public static int failFast1() {
+        ArrayList<Integer> numbers = new ArrayList<>();
+
+        numbers.add(10);
+        numbers.add(20);
+        numbers.add(30);
+        numbers.add(40);
+
+        Iterator<Integer> iterator = numbers.iterator();
+        while (iterator.hasNext()) {
+            Integer number = iterator.next();
+            numbers.add(50);
+        }
+
+        return numbers.size();
+    }
+
+    public static int failFast2() {
+        ArrayList<Integer> numbers = new ArrayList<>();
+        numbers.add(10);
+        numbers.add(20);
+        numbers.add(30);
+        numbers.add(40);
+
+        Iterator<Integer> iterator = numbers.iterator();
+        while (iterator.hasNext()) {
+            if (iterator.next() == 30) {
+                // will not throw Exception
+                iterator.remove();
+            }
+        }
+
+        System.out.println("using iterator's remove method = " + numbers);
+
+        iterator = numbers.iterator();
+        while (iterator.hasNext()) {
+            if (iterator.next() == 40) {
+                // will throw Exception on
+                // next call of next() method
+                numbers.remove(2);
+            }
+        }
+
+        return numbers.size();
+    }
+
+    public static int failSafe1() {
+        ConcurrentHashMap<String, Integer> map = new ConcurrentHashMap<>();
+
+        map.put("First", 10);
+        map.put("Second", 20);
+        map.put("Third", 30);
+        map.put("Fourth", 40);
+
+        Iterator<String> iterator = map.keySet()
+            .iterator();
+
+        while (iterator.hasNext()) {
+            String key = iterator.next();
+            map.put("Fifth", 50);
+        }
+
+        return map.size();
+    }
+
+}
@@ -1,8 +1,6 @@
-package com.baeldung.streamApi;
+package com.baeldung.stream;

 import java.util.List;
-import java.util.Optional;
-import java.util.stream.IntStream;
 import java.util.stream.Stream;

 /**
@@ -16,7 +16,7 @@ public class StreamApi {
    }
    
    public static String getLastElementUsingSkip(List<String> valueList) {
-        long count = valueList.stream().count();
+        long count = (long) valueList.size();
        Stream<String> stream = valueList.stream();
        return stream.skip(count - 1).findFirst().orElse(null);
    }
@@ -2,6 +2,7 @@ package com.baeldung.counter;

 import java.util.HashMap;
 import java.util.Map;
+import java.util.Random;

 import org.openjdk.jmh.annotations.Benchmark;
 import org.openjdk.jmh.annotations.BenchmarkMode;
@@ -18,8 +19,18 @@ public class CounterStatistics {
    private static final Map<String, MutableInteger> counterWithMutableIntMap = new HashMap<>();
    private static final Map<String, int[]> counterWithIntArrayMap = new HashMap<>();
    private static final Map<String, Long> counterWithLongWrapperMap = new HashMap<>();
+    private static final Map<String, Long> counterWithLongWrapperStreamMap = new HashMap<>();
+    
+    static {
+        CounterUtil.COUNTRY_NAMES = new String[10000];
+        final String prefix = "NewString"; 
+        Random random = new Random();
+        for (int i=0; i<10000; i++) {
+            CounterUtil.COUNTRY_NAMES[i] = new String(prefix + random.nextInt(1000));
+        }
+    }

-    @Benchmark
+  @Benchmark
    public void wrapperAsCounter() {
        CounterUtil.counterWithWrapperObject(counterMap);
    }
@@ -28,6 +39,11 @@ public class CounterStatistics {
    public void lambdaExpressionWithWrapper() {
        CounterUtil.counterWithLambdaAndWrapper(counterWithLongWrapperMap);
    }
+    
+    @Benchmark
+    public void parallelStreamWithWrapper() {
+        CounterUtil.counterWithParallelStreamAndWrapper(counterWithLongWrapperStreamMap);
+    }

    @Benchmark
    public void mutableIntegerAsCounter() {
@@ -6,7 +6,7 @@ import java.util.stream.Stream;

 public class CounterUtil {

-    private final static String[] COUNTRY_NAMES = { "China", "Australia", "India", "USA", "USSR", "UK", "China", "France", "Poland", "Austria", "India", "USA", "Egypt", "China" };
+    public static String[] COUNTRY_NAMES = { "China", "Australia", "India", "USA", "USSR", "UK", "China", "France", "Poland", "Austria", "India", "USA", "Egypt", "China" };

    public static void counterWithWrapperObject(Map<String, Integer> counterMap) {
        for (String country : COUNTRY_NAMES) {
@@ -15,9 +15,14 @@ public class CounterUtil {
    }

    public static void counterWithLambdaAndWrapper(Map<String, Long> counterMap) {
-        counterMap.putAll(Stream.of(COUNTRY_NAMES)
+        Stream.of(COUNTRY_NAMES)
+            .collect(Collectors.groupingBy(k -> k, () -> counterMap, Collectors.counting()));
+    }
+
+    public static void counterWithParallelStreamAndWrapper(Map<String, Long> counterMap) {
+        Stream.of(COUNTRY_NAMES)
            .parallel()
-            .collect(Collectors.groupingBy(k -> k, Collectors.counting())));
+            .collect(Collectors.groupingBy(k -> k, () -> counterMap, Collectors.counting()));
    }

    public static class MutableInteger {
@@ -49,4 +54,4 @@ public class CounterUtil {
        }
    }

-}
+}
@@ -4,7 +4,6 @@ import java.time.LocalDate;
 import java.time.LocalTime;
 import java.time.Month;

-import org.junit.Assert;
 import org.junit.Test;

 import static org.junit.Assert.assertEquals;
@@ -4,7 +4,6 @@ import java.time.DayOfWeek;
 import java.time.LocalDate;
 import java.time.LocalDateTime;

-import org.junit.Assert;
 import org.junit.Test;

 import static org.junit.Assert.assertEquals;
@@ -0,0 +1,79 @@
+package com.baeldung.defaultistaticinterfacemethods.test;
+
+import com.baeldung.defaultstaticinterfacemethods.model.Car;
+import com.baeldung.defaultstaticinterfacemethods.model.Motorbike;
+import com.baeldung.defaultstaticinterfacemethods.model.Vehicle;
+import org.junit.BeforeClass;
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.*;
+
+public class StaticDefaulInterfaceMethodUnitTest {
+
+    private static Car car;
+    private static Motorbike motorbike;
+
+    @BeforeClass
+    public static void setUpCarInstance() {
+        car = new Car("BMW");
+    }
+
+    @BeforeClass
+    public static void setUpMotorbikeInstance() {
+        motorbike = new Motorbike("Yamaha");
+    }
+
+    @Test
+    public void givenCarInstace_whenBrandisBMW_thenOneAssertion() {
+        assertThat(car.getBrand()).isEqualTo("BMW");
+    }
+
+    @Test
+    public void givenCarInstance_whenCallingSpeedUp_thenOneAssertion() {
+        assertThat(car.speedUp()).isEqualTo("The car is speeding up.");
+    }
+
+    @Test
+    public void givenCarInstance_whenCallingSlowDown_thenOneAssertion() {
+        assertThat(car.slowDown()).isEqualTo("The car is slowing down.");
+    }
+
+    @Test
+    public void givenCarInstance_whenCallingTurnAlarmOn_thenOneAssertion() {
+        assertThat(car.turnAlarmOn()).isEqualTo("Turning the vehice alarm on.");
+    }
+
+    @Test
+    public void givenCarInstance_whenCallingTurnAlarmOff_thenOneAssertion() {
+        assertThat(car.turnAlarmOff()).isEqualTo("Turning the vehicle alarm off.");
+    }
+
+    @Test
+    public void givenVehicleInterface_whenCallinggetHorsePower_thenOneAssertion() {
+        assertThat(Vehicle.getHorsePower(2500, 480)).isEqualTo(228);
+    }
+
+    @Test
+    public void givenMooorbikeInstace_whenBrandisYamaha_thenOneAssertion() {
+        assertThat(motorbike.getBrand()).isEqualTo("Yamaha");
+    }
+
+    @Test
+    public void givenMotorbikeInstance_whenCallingSpeedUp_thenOneAssertion() {
+        assertThat(motorbike.speedUp()).isEqualTo("The motorbike is speeding up.");
+    }
+
+    @Test
+    public void givenMotorbikeInstance_whenCallingSlowDown_thenOneAssertion() {
+        assertThat(motorbike.slowDown()).isEqualTo("The motorbike is slowing down.");
+    }
+
+    @Test
+    public void givenMotorbikeInstance_whenCallingTurnAlarmOn_thenOneAssertion() {
+        assertThat(motorbike.turnAlarmOn()).isEqualTo("Turning the vehice alarm on.");
+    }
+
+    @Test
+    public void givenMotorbikeInstance_whenCallingTurnAlarmOff_thenOneAssertion() {
+        assertThat(motorbike.turnAlarmOff()).isEqualTo("Turning the vehicle alarm off.");
+    }
+}
@@ -0,0 +1,40 @@
+package com.baeldung.iterators;
+
+import static com.baeldung.iterators.Iterators.failFast1;
+import static com.baeldung.iterators.Iterators.failFast2;
+import static com.baeldung.iterators.Iterators.failSafe1;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+import java.util.ConcurrentModificationException;
+
+import org.junit.Test;
+
+/**
+ * Source code https://github.com/eugenp/tutorials
+ *
+ * @author Santosh Thakur
+ */
+
+public class IteratorsTest {
+
+    @Test
+    public void whenFailFast_ThenThrowsException() {
+        assertThatThrownBy(() -> {
+            failFast1();
+        }).isInstanceOf(ConcurrentModificationException.class);
+    }
+
+    @Test
+    public void whenFailFast_ThenThrowsExceptionInSecondIteration() {
+        assertThatThrownBy(() -> {
+            failFast2();
+        }).isInstanceOf(ConcurrentModificationException.class);
+    }
+
+    @Test
+    public void whenFailSafe_ThenDoesNotThrowException() {
+        assertThat(failSafe1()).isGreaterThanOrEqualTo(0);
+    }
+
+}
@@ -1,6 +1,6 @@
 package com.baeldung.java8;

-import com.baeldung.streamApi.Product;
+import com.baeldung.stream.Product;
 import org.junit.Before;
 import org.junit.Test;
 import org.slf4j.Logger;
@@ -6,7 +6,6 @@ import java.util.Comparator;
 import org.junit.Before;
 import org.junit.Test;

-import lombok.Data;
 import static org.junit.Assert.assertTrue;

 public class Java8ComparatorUnitTest {
@@ -134,8 +133,7 @@ public class Java8ComparatorUnitTest {

    @Test
    public void whenThenComparing_thenSortedByAgeName() {
-        Comparator<Employee> employee_Age_Name_Comparator = Comparator.comparing(Employee::getAge)
-            .thenComparing(Employee::getName);
+        Comparator<Employee> employee_Age_Name_Comparator = Comparator.comparing(Employee::getAge).thenComparing(Employee::getName);

        Arrays.sort(someMoreEmployees, employee_Age_Name_Comparator);
        // System.out.println(Arrays.toString(someMoreEmployees));
@@ -144,8 +142,7 @@ public class Java8ComparatorUnitTest {

    @Test
    public void whenThenComparing_thenSortedByNameAge() {
-        Comparator<Employee> employee_Name_Age_Comparator = Comparator.comparing(Employee::getName)
-            .thenComparingInt(Employee::getAge);
+        Comparator<Employee> employee_Name_Age_Comparator = Comparator.comparing(Employee::getName).thenComparingInt(Employee::getAge);

        Arrays.sort(someMoreEmployees, employee_Name_Age_Comparator);
        // System.out.println(Arrays.toString(someMoreEmployees));
@@ -2,11 +2,11 @@ package com.baeldung.stream;

 import org.junit.Test;

-import java.util.ArrayList;
 import java.util.Arrays;
 import java.util.List;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
+import java.util.stream.Stream;

 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertTrue;
@@ -66,7 +66,9 @@ public class PrimitiveStreamsUnitTest {
    @Test
    public void givenAnArrayWhenSumIsCalledThenTheCorrectSumIsReturned() {

-        int sum = Arrays.asList(33,45).stream().mapToInt(a -> a).sum();
+        int sum = Stream.of(33,45)
+          .mapToInt(i -> i)
+          .sum();

        assertEquals(78, sum);
    }
@@ -0,0 +1,101 @@
+package com.baeldung.stringjoiner;
+
+import static org.junit.Assert.assertEquals;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.StringJoiner;
+import java.util.stream.Collectors;
+
+import org.junit.Test;
+
+public class StringJoinerUnitTest {
+    private final String DELIMITER_COMMA = ",";
+    private final String DELIMITER_HYPHEN = "-";
+    private final String PREFIX = "[";
+    private final String SUFFIX = "]";
+    private final String EMPTY_JOINER = "empty";
+
+    @Test
+    public void whenJoinerWithoutPrefixSuffixWithoutEmptyValue_thenReturnDefault() {
+        StringJoiner commaSeparatedJoiner = new StringJoiner(DELIMITER_COMMA);
+        assertEquals(0, commaSeparatedJoiner.toString().length());
+    }
+
+    @Test
+    public void whenJoinerWithPrefixSuffixWithoutEmptyValue_thenReturnDefault() {
+        StringJoiner commaSeparatedPrefixSuffixJoiner = new StringJoiner(DELIMITER_COMMA, PREFIX, SUFFIX);
+        assertEquals(commaSeparatedPrefixSuffixJoiner.toString(), PREFIX + SUFFIX);
+    }
+
+    @Test
+    public void whenJoinerWithoutPrefixSuffixWithEmptyValue_thenReturnDefault() {
+        StringJoiner commaSeparatedJoiner = new StringJoiner(DELIMITER_COMMA);
+        commaSeparatedJoiner.setEmptyValue(EMPTY_JOINER);
+
+        assertEquals(commaSeparatedJoiner.toString(), EMPTY_JOINER);
+    }
+
+    @Test
+    public void whenJoinerWithPrefixSuffixWithEmptyValue_thenReturnDefault() {
+        StringJoiner commaSeparatedPrefixSuffixJoiner = new StringJoiner(DELIMITER_COMMA, PREFIX, SUFFIX);
+        commaSeparatedPrefixSuffixJoiner.setEmptyValue(EMPTY_JOINER);
+
+        assertEquals(commaSeparatedPrefixSuffixJoiner.toString(), EMPTY_JOINER);
+    }
+
+    @Test
+    public void whenAddElements_thenJoinElements() {
+        StringJoiner rgbJoiner = new StringJoiner(DELIMITER_COMMA, PREFIX, SUFFIX);
+        rgbJoiner.add("Red")
+          .add("Green")
+          .add("Blue");
+
+        assertEquals(rgbJoiner.toString(), "[Red,Green,Blue]");
+    }
+
+    @Test
+    public void whenAddListElements_thenJoinListElements() {
+        List<String> rgbList = new ArrayList<String>();
+        rgbList.add("Red");
+        rgbList.add("Green");
+        rgbList.add("Blue");
+
+        StringJoiner rgbJoiner = new StringJoiner(DELIMITER_COMMA, PREFIX, SUFFIX);
+
+        for (String color : rgbList) {
+            rgbJoiner.add(color);
+        }
+
+        assertEquals(rgbJoiner.toString(), "[Red,Green,Blue]");
+    }
+
+    @Test
+    public void whenMergeJoiners_thenReturnMerged() {
+        StringJoiner rgbJoiner = new StringJoiner(DELIMITER_COMMA, PREFIX, SUFFIX);
+        StringJoiner cmybJoiner = new StringJoiner(DELIMITER_HYPHEN, PREFIX, SUFFIX);
+
+        rgbJoiner.add("Red")
+          .add("Green")
+          .add("Blue");
+        cmybJoiner.add("Cyan")
+          .add("Magenta")
+          .add("Yellow")
+          .add("Black");
+
+        rgbJoiner.merge(cmybJoiner);
+
+        assertEquals(rgbJoiner.toString(), "[Red,Green,Blue,Cyan-Magenta-Yellow-Black]");
+    }
+
+    @Test
+    public void whenUsedWithinCollectors_thenJoin() {
+        List<String> rgbList = Arrays.asList("Red", "Green", "Blue");
+        String commaSeparatedRGB = rgbList.stream()
+          .map(color -> color.toString())
+          .collect(Collectors.joining(","));
+
+        assertEquals(commaSeparatedRGB, "Red,Green,Blue");
+    }
+}
--- a/Show More
+++ b/Show More