Added test class for a simple shallow copy and deep copy

java-shallow-deep-copy/src/main/java/com/baeldung/java_shallow_deep_copy/data/Balance.java

@@ -0,0 +1,38 @@
+package com.baeldung.java_shallow_deep_copy.data;
+
+public class Balance implements Cloneable {
+
+    private float amount;
+    private String currency;
+
+    @Override
+    public Object clone() throws CloneNotSupportedException {
+        return super.clone();
+    }
+
+    public Balance(float amount, String currency) {
+        this.amount = amount;
+        this.currency = currency;
+    }
+
+    //Copy constructor
+    public Balance(Balance balance) {
+        this(balance.getAmount(), balance.getCurrency());
+    }
+
+    public float getAmount() {
+        return amount;
+    }
+
+    public void setAmount(float amount) {
+        this.amount = amount;
+    }
+
+    public String getCurrency() {
+        return currency;
+    }
+
+    public void setCurrency(String currency) {
+        this.currency = currency;
+    }
+}

java-shallow-deep-copy/src/main/java/com/baeldung/java_shallow_deep_copy/data/BankAccount.java

@@ -0,0 +1,38 @@
+package com.baeldung.java_shallow_deep_copy.data;
+
+public class BankAccount implements Cloneable {
+
+    protected String name;
+    protected String surname;
+    protected Balance balance;
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public String getSurname() {
+        return surname;
+    }
+
+    public void setSurname(String surname) {
+        this.surname = surname;
+    }
+
+    public Balance getBalance() {
+        return balance;
+    }
+
+    public void setBalance(Balance balance) {
+        this.balance = balance;
+    }
+
+    public BankAccount(String name, String surname, Balance balance) {
+        this.name = name;
+        this.surname = surname;
+        this.balance = balance;
+    }
+}

java-shallow-deep-copy/src/main/java/com/baeldung/java_shallow_deep_copy/data/BankAccountDeep.java

@@ -0,0 +1,17 @@
+package com.baeldung.java_shallow_deep_copy.data;
+
+public class BankAccountDeep extends BankAccount {
+
+    public BankAccountDeep(String name, String surname, Balance balance) {
+        super(name, surname, balance);
+    }
+
+    @Override
+    public Object clone() throws CloneNotSupportedException {
+        return new BankAccountDeep(name, surname, (Balance) balance.clone());
+    }
+
+    public BankAccountDeep(BankAccountDeep bankAccountDeep) {
+        this(bankAccountDeep.name, bankAccountDeep.surname, new Balance(bankAccountDeep.balance));
+    }
+}

java-shallow-deep-copy/src/main/java/com/baeldung/java_shallow_deep_copy/data/BankAccountShallow.java

@@ -0,0 +1,17 @@
+package com.baeldung.java_shallow_deep_copy.data;
+
+public class BankAccountShallow extends BankAccount {
+
+    public BankAccountShallow(String name, String surname, Balance balance) {
+        super(name, surname, balance);
+    }
+
+    public BankAccountShallow(BankAccountShallow shallow) {
+        this(shallow.name, shallow.surname, shallow.balance);
+    }
+
+    @Override
+    public Object clone() throws CloneNotSupportedException {
+        return super.clone();
+    }
+}

java-shallow-deep-copy/src/main/java/com/baeldung/java_shallow_deep_copy/data/Person.java

@@ -1,34 +0,0 @@
-package com.baeldung.java_shallow_deep_copy.data;
-
-import java.util.List;
-
-public class Person {
-
-    private String name;
-    private String surname;
-    private List<String> addresses;
-
-    public String getName() {
-        return name;
-    }
-
-    public void setName(String name) {
-        this.name = name;
-    }
-
-    public String getSurname() {
-        return surname;
-    }
-
-    public void setSurname(String surname) {
-        this.surname = surname;
-    }
-
-    public List<String> getAddresses() {
-        return addresses;
-    }
-
-    public void setAddresses(List<String> addresses) {
-        this.addresses = addresses;
-    }
-}

java-shallow-deep-copy/src/main/java/com/baeldung/java_shallow_deep_copy/data/PersonDeep.java

@@ -1,15 +0,0 @@
-package com.baeldung.java_shallow_deep_copy.data;
-
-import java.util.ArrayList;
-import java.util.List;
-
-public class PersonDeep  extends Person{
-
-    public PersonDeep(String name, String surname, List<String> addresses) {
-        this.setName(name);
-        this.setSurname(surname);
-        List<String> deepCopyList = new ArrayList<>();
-        deepCopyList.addAll(addresses);
-        this.setAddresses(deepCopyList);
-    }
-}

java-shallow-deep-copy/src/main/java/com/baeldung/java_shallow_deep_copy/data/PersonShallow.java

@@ -1,14 +0,0 @@
-package com.baeldung.java_shallow_deep_copy.data;
-
-import java.util.List;
-
-public class PersonShallow extends Person {
-
-    public PersonShallow(String name, String surname, List<String> addresses) {
-        this.setName(name);
-        this.setSurname(surname);
-        this.setAddresses(addresses);
-    }
-
-
-}

java-shallow-deep-copy/src/test/java/com/baeldung/java_shallow_deep_copy/unit/DeepCopyTest.java

@@ -1,26 +1,53 @@
 package com.baeldung.java_shallow_deep_copy.unit;
 
-import com.baeldung.java_shallow_deep_copy.data.PersonDeep;
+import com.baeldung.java_shallow_deep_copy.data.*;
-import com.baeldung.java_shallow_deep_copy.data.PersonShallow;
+
-import org.junit.jupiter.api.Assertions;
 import org.junit.jupiter.api.Test;
 
-import java.util.ArrayList;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
-import java.util.List;
 
 public class DeepCopyTest {
 
+    private static final String NAME = "Hello";
+    private static final String SURNAME = "World";
+
     @Test
-    void whenTheParameterIsNotAnImmutableObject_thenShouldDoADeepCopy (){
+    void whenIsADeepCopyDoneByCopyConstructor_thenNestedObjectShouldNotHaveSameReference() {
+        Balance balance = new Balance(10000, "EUR");
+        BankAccountDeep bankAccount = new BankAccountDeep(NAME, SURNAME, balance);
+        BankAccountDeep deepCopy = new BankAccountDeep(bankAccount);
+        assertNotEquals(bankAccount.getBalance(), deepCopy.getBalance());
+    }
+
+    @Test
+    void whenIsADeepCopyDoneByCopyConstructor_thenCopyValueShouldNotChange() {
+        Balance balance = new Balance(10000, "EUR");
+        BankAccountDeep bankAccount = new BankAccountDeep(NAME, SURNAME, balance);
+        BankAccountDeep deepCopy = new BankAccountDeep(bankAccount);
+        balance.setAmount(0);
+        assertNotEquals(bankAccount.getBalance()
+          .getAmount(), deepCopy.getBalance()
+          .getAmount());
+    }
+
+    @Test
+    void whenIsADeepCopyDoneByCloneMethod_thenNestedObjectShouldNotHaveSameReference() throws CloneNotSupportedException {
         String name = "Hello";
         String surname = "World";
-        List<String> addresses = new ArrayList<>();
+        Balance balance = new Balance(10000, "EUR");
-        addresses.add("Standford street");
+        BankAccountDeep bankAccount = new BankAccountDeep(NAME, SURNAME, balance);
-        PersonDeep personShallow = new PersonDeep(name,surname,addresses);
+        BankAccountDeep deepCopy = (BankAccountDeep) bankAccount.clone();
-        personShallow.getAddresses().forEach(System.out :: println);
+        assertNotEquals(bankAccount.getBalance(), deepCopy.getBalance());
-        Assertions.assertEquals(addresses, personShallow.getAddresses());
+    }
-        addresses.add("Oxford street");
+
-        personShallow.getAddresses().forEach(System.out :: println);
+    @Test
-        Assertions.assertNotEquals(addresses, personShallow.getAddresses());
+    void whenIsADeepCopyDoneByCloneMethod_thenCopyValueShouldNotChange() throws CloneNotSupportedException {
+
+        Balance balance = new Balance(10000, "EUR");
+        BankAccountDeep bankAccount = new BankAccountDeep(NAME, SURNAME, balance);
+        BankAccountDeep deepCopy = (BankAccountDeep) bankAccount.clone();
+        balance.setAmount(0);
+        assertNotEquals(balance.getAmount(), deepCopy.getBalance()
+          .getAmount());
     }
 }

java-shallow-deep-copy/src/test/java/com/baeldung/java_shallow_deep_copy/unit/ShallowCopyTest.java

@@ -1,38 +1,62 @@
 package com.baeldung.java_shallow_deep_copy.unit;
 
-import com.baeldung.java_shallow_deep_copy.data.PersonShallow;
+import com.baeldung.java_shallow_deep_copy.data.Balance;
-import org.junit.jupiter.api.Assertions;
+import com.baeldung.java_shallow_deep_copy.data.BankAccountShallow;
+
 import org.junit.jupiter.api.Test;
 
-import java.util.ArrayList;
+import static org.junit.jupiter.api.Assertions.assertEquals;
-import java.util.List;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
-
 
 public class ShallowCopyTest {
 
     @Test
-    void whenTheParameterIsAnImmutableObject_thenShouldNotChangeTheValue (){
+    void whenIsAShallowCopyDoneByCopyConstructor_thenImmutableObjectWillNotChange() {
         String name = "Hello";
         String surname = "World";
-        PersonShallow personShallow = new PersonShallow(name,surname,null);
+        BankAccountShallow personShallow = new BankAccountShallow(name, surname, null);
         surname = "Pluto";
-        Assertions.assertNotEquals(surname, personShallow.getSurname());
+        assertNotEquals(surname, personShallow.getSurname());
     }
 
     @Test
-    void whenTheParameterIsNotAnImmutableObject_thenShouldDoAShallowCopy (){
+    void whenIsAShallowCopyDoneByCopyConstructor_thenNestedObjectsAreTheSame() {
-        String name = "Hello";
+        Balance balance = new Balance(10000, "EUR");
-        String surname = "World";
+        BankAccountShallow bankAccount = new BankAccountShallow("Hello", "World", balance);
-        List<String> addresses = new ArrayList<>();
+        BankAccountShallow shallowCopy = new BankAccountShallow(bankAccount.getName(), bankAccount.getSurname(), bankAccount.getBalance());
-        addresses.add("Standford street");
+        assertEquals(bankAccount.getBalance(), shallowCopy.getBalance());
-        PersonShallow personShallow = new PersonShallow(name,surname,addresses);
-        personShallow.getAddresses().forEach(System.out :: println);
-        Assertions.assertEquals(addresses, personShallow.getAddresses());
-        addresses.add("Oxford street");
-        personShallow.getAddresses().forEach(System.out :: println);
-        Assertions.assertEquals(addresses, personShallow.getAddresses());
     }
 
+    @Test
+    void whenIsAShallowCopyDoneByCopyConstructor_thenCopyValueShouldChange() throws CloneNotSupportedException {
+        Balance balance = new Balance(10000, "EUR");
+        BankAccountShallow bankAccount = new BankAccountShallow("Hello", "World", balance);
+        BankAccountShallow shallowCopy = new BankAccountShallow(bankAccount);
+        float newBalance = 0;
+        balance.setAmount(newBalance);
+        assertEquals(newBalance, bankAccount.getBalance()
+          .getAmount());
+        assertEquals(newBalance, shallowCopy.getBalance()
+          .getAmount());
+    }
 
+    @Test
+    void whenIsAShallowCopyDoneByCloneMethod_thenNestedObjectsAreTheSame() throws CloneNotSupportedException {
+        Balance balance = new Balance(10000, "EUR");
+        BankAccountShallow bankAccount = new BankAccountShallow("Hello", "World", balance);
+        BankAccountShallow shallowCopy = (BankAccountShallow) bankAccount.clone();
+        assertEquals(bankAccount.getBalance(), shallowCopy.getBalance());
+    }
+
+    @Test
+    void whenIsAShallowCopyDoneByCloneMethod__thenCopyValueShouldChange() throws CloneNotSupportedException {
+        Balance balance = new Balance(10000, "EUR");
+        BankAccountShallow bankAccount = new BankAccountShallow("Hello", "World", balance);
+        BankAccountShallow shallowCopy = (BankAccountShallow) bankAccount.clone();
+        float newBalance = 0;
+        balance.setAmount(newBalance);
+        assertEquals(newBalance, shallowCopy.getBalance()
+          .getAmount());
+    }
 
 }