[JAVA-616] core-java-arrays-operations-advanced

* Creation

* Moved code from https://www.baeldung.com/java-array-copy

* Moved code from https://www.baeldung.com/java-arrays-deepequals

* Moved code from https://www.baeldung.com/java-array-sum-average

* Moved code from https://www.baeldung.com/java-array-intersection

core-java-modules/core-java-arrays-operations-advanced/README.md

@@ -0,0 +1,16 @@
+## Core Java Arrays - Advanced Operations
+
+This module contains articles about advanced operations on arrays in Java
+
+Advanced operations would be much logic or interactions with other arrays, such as:
+
+- Sum, average of elements
+- Intersections
+- ...
+
+### Relevant Articles: 
+- [How to Copy an Array in Java](https://www.baeldung.com/java-array-copy)
+- [Arrays.deepEquals](https://www.baeldung.com/java-arrays-deepequals)
+- [Find Sum and Average in a Java Array](https://www.baeldung.com/java-array-sum-average)
+- [Intersection Between two Integer Arrays](https://www.baeldung.com/java-array-intersection)
+- [[More basic operations-->]](/core-java-modules/core-java-operations-basic)

core-java-modules/core-java-arrays-operations-advanced/pom.xml

@@ -0,0 +1,36 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0"
+         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+    <parent>
+        <artifactId>core-java-modules</artifactId>
+        <groupId>com.baeldung.core-java-modules</groupId>
+        <version>1.0.0-SNAPSHOT</version>
+    </parent>
+    <modelVersion>4.0.0</modelVersion>
+
+    <artifactId>core-java-arrays-operations-advanced</artifactId>
+    <name>core-java-arrays-operations-advanced</name>
+    <packaging>jar</packaging>
+
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+
+        <dependency>
+            <groupId>org.assertj</groupId>
+            <artifactId>assertj-core</artifactId>
+            <version>${assertj-core.version}</version>
+            <scope>test</scope>
+        </dependency>
+    </dependencies>
+
+    <properties>
+        <commons-lang3.version>3.9</commons-lang3.version>
+
+        <assertj-core.version>3.10.0</assertj-core.version>
+    </properties>
+</project>

core-java-modules/core-java-arrays-operations-advanced/src/main/java/com/baeldung/array/SumAndAverageInArray.java

@@ -0,0 +1,31 @@
+package com.baeldung.array;
+
+import java.util.Arrays;
+
+public class SumAndAverageInArray {
+
+    public static int findSumWithoutUsingStream(int[] array) {
+        int sum = 0;
+        for (int value : array) {
+            sum += value;
+        }
+        return sum;
+    }
+
+    public static int findSumUsingStream(int[] array) {
+        return Arrays.stream(array).sum();
+    }
+
+    public static int findSumUsingStream(Integer[] array) {
+        return Arrays.stream(array).mapToInt(Integer::intValue).sum();
+    }
+
+    public static double findAverageWithoutUsingStream(int[] array) {
+        int sum = findSumWithoutUsingStream(array);
+        return (double) sum / array.length;
+    }
+
+    public static double findAverageUsingStream(int[] array) {
+        return Arrays.stream(array).average().orElse(Double.NaN);
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/main/java/com/baeldung/array/operations/ArraysIntersectionOperations.java

@@ -0,0 +1,27 @@
+package com.baeldung.array.operations;
+
+import java.util.Arrays;
+import java.util.LinkedList;
+import java.util.stream.Stream;
+
+public class ArraysIntersectionOperations {
+
+    public static Integer[] intersectionSimple(final Integer[] a, final Integer[] b) {
+        return Stream.of(a)
+            .filter(Arrays.asList(b)::contains)
+            .toArray(Integer[]::new);
+    }
+
+    public static Integer[] intersectionSet(final Integer[] a, final Integer[] b) {
+        return Stream.of(a)
+            .filter(Arrays.asList(b)::contains)
+            .distinct()
+            .toArray(Integer[]::new);
+    }
+
+    public static Integer[] intersectionMultiSet(final Integer[] a, final Integer[] b) {
+        return Stream.of(a)
+            .filter(new LinkedList<>(Arrays.asList(b))::remove)
+            .toArray(Integer[]::new);
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/main/java/com/baeldung/arraycopy/model/Address.java

@@ -0,0 +1,61 @@
+package com.baeldung.arraycopy.model;
+
+public class Address implements Cloneable {
+    private String country;
+    private String state;
+    private String city;
+    private String street;
+    private String zipcode;
+
+    public String getCountry() {
+        return country;
+    }
+
+    public void setCountry(String country) {
+        this.country = country;
+    }
+
+    public String getState() {
+        return state;
+    }
+
+    public void setState(String state) {
+        this.state = state;
+    }
+
+    public String getCity() {
+        return city;
+    }
+
+    public void setCity(String city) {
+        this.city = city;
+    }
+
+    public String getStreet() {
+        return street;
+    }
+
+    public void setStreet(String street) {
+        this.street = street;
+    }
+
+    public String getZipcode() {
+        return zipcode;
+    }
+
+    public void setZipcode(String zipcode) {
+        this.zipcode = zipcode;
+    }
+
+    @Override
+    protected Object clone() throws CloneNotSupportedException {
+        super.clone();
+        Address address = new Address();
+        address.setCity(this.city);
+        address.setCountry(this.country);
+        address.setState(this.state);
+        address.setStreet(this.street);
+        address.setZipcode(this.zipcode);
+        return address;
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/main/java/com/baeldung/arraycopy/model/Employee.java

@@ -0,0 +1,48 @@
+package com.baeldung.arraycopy.model;
+
+import java.io.Serializable;
+
+public class Employee implements Serializable {
+    private static final long serialVersionUID = -2454619097207585825L;
+    private int id;
+    private String name;
+    private int age;
+
+    public Employee() {
+    }
+
+    public Employee(int id, String name) {
+        this.id = id;
+        this.name = name;
+    }
+
+    public Employee(int id, String name, int age) {
+        this.id = id;
+        this.name = name;
+        this.age = age;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public int getId() {
+        return id;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    public void setId(int id) {
+        this.id = id;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/array/SumAndAverageInArrayUnitTest.java

@@ -0,0 +1,59 @@
+package com.baeldung.array;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class SumAndAverageInArrayUnitTest {
+    @Test
+    public void givenAnIntArray_whenNotUsingStream_thenFindSum() {
+        int[] array = { 1, 3, 4, 8, 19, 20 };
+        int expectedSumOfArray = 55;
+        int actualSumOfArray = SumAndAverageInArray.findSumWithoutUsingStream(array);
+        Assert.assertEquals(expectedSumOfArray, actualSumOfArray);
+    }
+
+    @Test
+    public void givenAnIntArray_whenUsingStream_thenFindSum() {
+        int[] array = { 1, 3, 4, 8, 19, 20 };
+        int expectedSumOfArray = 55;
+        int actualSumOfArray = SumAndAverageInArray.findSumUsingStream(array);
+
+        Assert.assertEquals(expectedSumOfArray, actualSumOfArray);
+    }
+
+    @Test
+    public void givenAnBoxedIntegerArray_whenUsingStream_thenFindSum() {
+        Integer[] array = new Integer[]{1, 3, 4, 8, 19, 20};
+        int expectedSumOfArray = 55;
+        int actualSumOfArray = SumAndAverageInArray.findSumUsingStream(array);
+
+        Assert.assertEquals(expectedSumOfArray, actualSumOfArray);
+    }
+
+    @Test
+    public void givenAnIntArray_whenNotUsingStream_thenFindAverage() {
+        int[] array = { 1, 3, 4, 8, 19, 20 };
+        double expectedAvgOfArray = 9.17;
+        double actualAvgOfArray = SumAndAverageInArray.findAverageWithoutUsingStream(array);
+
+        Assert.assertEquals(expectedAvgOfArray, actualAvgOfArray, 0.0034);
+    }
+
+    @Test
+    public void givenAnIntArray_whenUsingStream_thenFindAverage() {
+        int[] array = { 1, 3, 4, 8, 19, 20 };
+        double expectedAvgOfArray = 9.17;
+        double actualAvgOfArray = SumAndAverageInArray.findAverageUsingStream(array);
+
+        Assert.assertEquals(expectedAvgOfArray, actualAvgOfArray, 0.0034);
+    }
+
+    @Test
+    public void givenAnEmptyIntArray_whenUsingStream_thenFindAverage() {
+        int[] array = {};
+        double expectedAvgOfArray = Double.NaN;
+        double actualAvgOfArray = SumAndAverageInArray.findAverageUsingStream(array);
+
+        Assert.assertEquals(expectedAvgOfArray, actualAvgOfArray, 0.00);
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/array/operations/IntersectionUnitTest.java

@@ -0,0 +1,64 @@
+package com.baeldung.array.operations;
+
+import org.junit.jupiter.api.Test;
+
+import static com.baeldung.array.operations.ArraysIntersectionOperations.*;
+import static org.assertj.core.api.Assertions.assertThat;
+
+class IntersectionUnitTest {
+    private static final Integer[] a = { 1, 3, 2 };
+    private static final Integer[] b = { 4, 3, 2, 4, 2, 3, 4, 4, 3 };
+    private static final Integer[] c = { 1, 3, 2, 3, 3, 2 };
+
+    @Test
+    void whenIntersectionSimpleIsUsed_thenCommonEntriesAreInTheResult() {
+        assertThat(intersectionSimple(a, b)).isEqualTo(new Integer[] { 3, 2 });
+        assertThat(intersectionSimple(b, a)).isEqualTo(new Integer[] { 3, 2, 2, 3, 3 });
+    }
+
+    @Test
+    void whenIntersectionSimpleIsUsedWithAnArrayAndItself_thenTheResultIsTheIdentity() {
+        assertThat(intersectionSimple(b, b)).isEqualTo(b);
+        assertThat(intersectionSimple(a, a)).isEqualTo(a);
+    }
+
+    @Test
+    void whenIntersectionSetIsUsed_thenCommonEntriesAreInTheResult() {
+        assertThat(intersectionSet(b, a)).isEqualTo(new Integer[] { 3, 2 });
+    }
+
+    @Test
+    void whenIntersectionSetIsUsed_thenTheNumberOfEntriesDoesNotChangeWithTheParameterOrder() {
+        assertThat(intersectionSet(a, b)).isEqualTo(new Integer[] { 3, 2 });
+        assertThat(intersectionSet(b, a)).isEqualTo(new Integer[] { 3, 2 });
+    }
+
+    @Test
+    void whenIntersectionSetIsUsedWithAnArrayAndWithItself_andTheInputHasNoDuplicateEntries_ThenTheResultIsTheIdentity() {
+        assertThat(intersectionSet(a, a)).isEqualTo(a);
+    }
+
+    @Test
+    void whenIntersectionSetIsUsedWithAnArrayAndWithItself_andTheInputHasDuplicateEntries_ThenTheResultIsNotTheIdentity() {
+        assertThat(intersectionSet(b, b)).isNotEqualTo(b);
+    }
+
+    @Test
+    void whenMultiSetIsUsed_thenCommonEntriesAreInTheResult() {
+        assertThat(intersectionMultiSet(b, a)).isEqualTo(new Integer[] { 3, 2 });
+    }
+
+    @Test
+    void whenIntersectionMultiSetIsUsed_thenTheNumberOfEntriesDoesNotChangeWithTheParameterOrder() {
+        assertThat(intersectionMultiSet(a, b)).isEqualTo(new Integer[] { 3, 2 });
+        assertThat(intersectionMultiSet(b, a)).isEqualTo(new Integer[] { 3, 2 });
+        assertThat(intersectionMultiSet(b, c)).isEqualTo(new Integer[] { 3, 2, 2, 3, 3 });
+        assertThat(intersectionMultiSet(c, b)).isEqualTo(new Integer[] { 3, 2, 3, 3, 2 });
+    }
+
+    @Test
+    void whenIntersectionMultiSetIsUsedWithAnArrayAndWithItself_ThenTheResultIsTheIdentity() {
+        assertThat(intersectionMultiSet(b, b)).isEqualTo(b);
+        assertThat(intersectionMultiSet(a, a)).isEqualTo(a);
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arraycopy/ArrayCopyUtilUnitTest.java

@@ -0,0 +1,170 @@
+package com.baeldung.arraycopy;
+
+import com.baeldung.arraycopy.model.Address;
+import com.baeldung.arraycopy.model.Employee;
+import org.apache.commons.lang3.SerializationUtils;
+import org.junit.Assert;
+import org.junit.BeforeClass;
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static org.junit.Assert.assertTrue;
+
+public class ArrayCopyUtilUnitTest {
+    private static Employee[] employees;
+    private static final int MAX = 2;
+
+    @BeforeClass
+    public static void setup(){
+      createEmployeesArray();
+    }
+
+    private static void createEmployeesArray() {
+        employees = new Employee[MAX];
+          Employee employee;
+          for(int i = 0; i < MAX; i++) {
+              employee = new Employee();
+              employee.setName("Emp"+i);
+              employee.setId(i);
+              employees[i] = employee;
+          }
+    }
+
+    @Test
+    public void givenArrayOfPrimitiveType_whenCopiedViaSystemsArrayCopy_thenSuccessful(){
+        int[] array = {23, 43, 55};
+        int[] copiedArray = new int[3];
+        
+        System.arraycopy(array, 0, copiedArray, 0, 3);
+        
+        Assert.assertArrayEquals(copiedArray, array);
+    }
+
+    @Test
+    public void givenArrayOfPrimitiveType_whenCopiedSubSequenceViaSystemsArrayCopy_thenSuccessful(){
+        int[] array = {23, 43, 55, 12, 65, 88, 92};
+        int[] copiedArray = new int[3];
+        
+        System.arraycopy(array, 2, copiedArray, 0, 3);
+        
+        assertTrue(3 == copiedArray.length);
+        assertTrue(copiedArray[0] == array[2]);
+        assertTrue(copiedArray[1] == array[3]);
+        assertTrue(copiedArray[2] == array[4]);
+    }
+
+    @Test
+    public void givenArrayOfPrimitiveType_whenCopiedSubSequenceViaArraysCopyOfRange_thenSuccessful(){
+        int[] array = {23, 43, 55, 12, 65, 88, 92};
+        
+        int[] copiedArray = Arrays.copyOfRange(array, 1, 4);
+        
+        assertTrue(3 == copiedArray.length);
+        assertTrue(copiedArray[0] == array[1]);
+        assertTrue(copiedArray[1] == array[2]);
+        assertTrue(copiedArray[2] == array[3]);
+    }
+
+    @Test
+    public void givenArrayOfPrimitiveType_whenCopiedViaArraysCopyOf_thenValueChangeIsSuccessful(){
+        int[] array = {23, 43, 55, 12};
+        int newLength = array.length;
+        
+        int[] copiedArray = Arrays.copyOf(array, newLength);
+        
+        Assert.assertArrayEquals(copiedArray, array);
+        array[0] = 9;
+        assertTrue(copiedArray[0] != array[0]);
+        copiedArray[1] = 12;
+        assertTrue(copiedArray[1] != array[1]);
+    }
+
+    @Test
+    public void givenArrayOfNonPrimitiveType_whenCopiedViaArraysCopyOf_thenDoShallowCopy(){
+        Employee[] copiedArray = Arrays.copyOf(employees, employees.length);
+        
+        Assert.assertArrayEquals(copiedArray, employees);
+        employees[0].setName(employees[0].getName()+"_Changed");
+        //change in employees' element caused change in the copied array
+        assertTrue(copiedArray[0].getName().equals(employees[0].getName()));
+    }
+
+    @Test
+    public void givenArrayOfPrimitiveType_whenCopiedViaArrayClone_thenValueChangeIsSuccessful(){
+        int[] array = {23, 43, 55, 12};
+        
+        int[] copiedArray = array.clone();
+        
+        Assert.assertArrayEquals(copiedArray, array);
+        array[0] = 9;
+        assertTrue(copiedArray[0] != array[0]);
+        copiedArray[1] = 12;
+        assertTrue(copiedArray[1] != array[1]);
+    }
+
+    @Test
+    public void givenArraysOfNonPrimitiveType_whenCopiedViaArrayClone_thenDoShallowCopy(){
+        Employee[] copiedArray = employees.clone();
+        
+        Assert.assertArrayEquals(copiedArray, employees);;
+        employees[0].setName(employees[0].getName()+"_Changed");
+        //change in employees' element changed the copied array
+        assertTrue(copiedArray[0].getName().equals(employees[0].getName()));
+    }
+
+    @Test
+    public void givenArraysOfCloneableNonPrimitiveType_whenCopiedViaArrayClone_thenDoShallowCopy(){
+        Address[] addresses = createAddressArray();
+        
+        Address[] copiedArray = addresses.clone();
+        
+        addresses[0].setCity(addresses[0].getCity()+"_Changed");
+        Assert.assertArrayEquals(copiedArray, addresses);
+    }
+
+    @Test
+    public void givenArraysOfSerializableNonPrimitiveType_whenCopiedViaSerializationUtils_thenDoDeepCopy(){
+        Employee[] copiedArray = SerializationUtils.clone(employees);
+       
+        employees[0].setName(employees[0].getName()+"_Changed");
+        //change in employees' element didn't change in the copied array
+        Assert.assertFalse(
+            copiedArray[0].getName().equals(employees[0].getName()));
+    }
+    
+    @Test
+    public void givenArraysOfNonPrimitiveType_whenCopiedViaStream_thenDoShallowCopy(){
+        Employee[] copiedArray = Arrays.stream(employees).toArray(Employee[]::new);
+        
+        Assert.assertArrayEquals(copiedArray, employees);
+        employees[0].setName(employees[0].getName()+"_Changed");
+        //change in employees' element didn't change in the copied array
+        assertTrue(copiedArray[0].getName().equals(employees[0].getName()));
+    }
+    
+    @Test
+    public void givenArraysOfPrimitiveType_whenCopiedViaStream_thenSuccessful(){
+        String[] strArray = {"orange", "red", "green'"};
+        
+        String[] copiedArray = Arrays.stream(strArray).toArray(String[]::new);
+        
+        Assert.assertArrayEquals(copiedArray, strArray);
+    }
+    
+    private Address[] createAddressArray(){
+        Address[] addresses = new Address[1];
+        addresses[0] = createAddress();
+        return addresses;
+    }
+
+    private Address createAddress() {
+        Address address = new Address();
+        address.setCountry("USA");
+        address.setState("CA");
+        address.setCity("San Francisco");
+        address.setStreet("Street 1");
+        address.setZipcode("59999");
+        return address;
+    }
+}

core-java-modules/core-java-arrays-operations-advanced/src/test/java/com/baeldung/arrays/deepequals/ArraysDeepEqualsUnitTest.java

@@ -0,0 +1,96 @@
+package com.baeldung.arrays.deepequals;
+
+import static org.junit.Assert.assertFalse;
+import static org.junit.Assert.assertTrue;
+
+import java.util.Arrays;
+import java.util.Objects;
+import org.junit.jupiter.api.Test;
+
+public class ArraysDeepEqualsUnitTest {
+
+    class Person {
+        private int id;
+        private String name;
+        private int age;
+
+        Person(int id, String name, int age) {
+            this.id = id;
+            this.name = name;
+            this.age = age;
+        }
+
+        @Override
+        public boolean equals(Object obj) {
+            if (this == obj) {
+                return true;
+            }
+            if (obj == null) {
+                return false;
+            }
+            if (!(obj instanceof Person))
+                return false;
+            Person person = (Person) obj;
+            return id == person.id && name.equals(person.name) && age == person.age;
+        }
+
+        @Override
+        public int hashCode() {
+            return Objects.hash(id, name, age);
+        }
+    }
+
+    @Test
+    void givenTwoUnidimensionalObjectTypeArrays_whenUsingEqualsAndDeepEquals_thenBothShouldReturnTrue() {
+        Object[] anArray = new Object[] { "string1", "string2", "string3" };
+        Object[] anotherArray = new Object[] { "string1", "string2", "string3" };
+
+        assertTrue(Arrays.equals(anArray, anotherArray));
+        assertTrue(Arrays.deepEquals(anArray, anotherArray));
+    }
+
+    @Test
+    void givenTwoUnidimensionalObjectTypeArraysWithNullElements_whenUsingEqualsAndDeepEquals_thenBothShouldReturnTrue() {
+        Object[] anArray = new Object[] { "string1", null, "string3" };
+        Object[] anotherArray = new Object[] { "string1", null, "string3" };
+
+        assertTrue(Arrays.equals(anArray, anotherArray));
+        assertTrue(Arrays.deepEquals(anArray, anotherArray));
+    }
+
+    @Test
+    void givenTwoUnidimensionalObjectTypeArraysWithNestedElements_whenUsingEqualsAndDeepEquals_thenShouldReturnDifferently() {
+        Object[] anArray = new Object[] { "string1", null, new String[] { "nestedString1", "nestedString2" } };
+        Object[] anotherArray = new Object[] { "string1", null, new String[] { "nestedString1", "nestedString2" } };
+
+        assertFalse(Arrays.equals(anArray, anotherArray));
+        assertTrue(Arrays.deepEquals(anArray, anotherArray));
+    }
+
+    @Test
+    void givenTwoMultidimensionalPrimitiveTypeArrays_whenUsingEqualsAndDeepEquals_thenBothShouldReturnDifferently() {
+        int[][] anArray = { { 1, 2, 3 }, { 4, 5, 6, 9 }, { 7 } };
+        int[][] anotherArray = { { 1, 2, 3 }, { 4, 5, 6, 9 }, { 7 } };
+
+        assertFalse(Arrays.equals(anArray, anotherArray));
+        assertTrue(Arrays.deepEquals(anArray, anotherArray));
+    }
+
+    @Test
+    void givenTwoMultidimensionalObjectTypeArrays_whenUsingEqualsAndDeepEquals_thenBothShouldReturnDifferently() {
+        Person personArray1[][] = { { new Person(1, "John", 22), new Person(2, "Mike", 23) }, { new Person(3, "Steve", 27), new Person(4, "Gary", 28) } };
+        Person personArray2[][] = { { new Person(1, "John", 22), new Person(2, "Mike", 23) }, { new Person(3, "Steve", 27), new Person(4, "Gary", 28) } };
+
+        assertFalse(Arrays.equals(personArray1, personArray2));
+        assertTrue(Arrays.deepEquals(personArray1, personArray2));
+    }
+
+    @Test
+    void givenTwoMultidimensionalObjectTypeArrays_whenUsingDeepEqualsFromObjectsAndArraysClasses_thenBothShouldReturnTrue() {
+        Person personArray1[][] = { { new Person(1, "John", 22), new Person(2, "Mike", 23) }, { new Person(3, "Steve", 27), new Person(4, "Gary", 28) } };
+        Person personArray2[][] = { { new Person(1, "John", 22), new Person(2, "Mike", 23) }, { new Person(3, "Steve", 27), new Person(4, "Gary", 28) } };
+
+        assertTrue(Objects.deepEquals(personArray1, personArray2));
+        assertTrue(Arrays.deepEquals(personArray1, personArray2));
+    }
+}