Creating shallow copy vs deep copy in Java

core-java-modules/core-java-lang-oop-patterns/src/main/java/com/baeldung/shallowvsdeepcopy/Address.java

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+package com.baeldung.shallowvsdeepcopy;
+
+class Address implements Cloneable{
+
+    private String streetName;
+    private String zipCode;
+    private String cityName;
+    private String country;
+
+    public Address(String streetName, String zipCode, String cityName, String country) {
+        this.streetName = streetName;
+        this.zipCode = zipCode;
+        this.cityName = cityName;
+        this.country = country;
+    }
+
+    public String getStreetName() {
+        return streetName;
+    }
+
+    public void setStreetName(String streetName) {
+        this.streetName = streetName;
+    }
+
+    public String getZipCode() {
+        return zipCode;
+    }
+
+    public void setZipCode(String zipCode) {
+        this.zipCode = zipCode;
+    }
+
+    public String getCityName() {
+        return cityName;
+    }
+
+    public void setCityName(String cityName) {
+        this.cityName = cityName;
+    }
+
+    public String getCountry() {
+        return country;
+    }
+
+    public void setCountry(String country) {
+        this.country = country;
+    }
+
+    @Override
+    public Address clone() {
+        try {
+            Address clone = (Address) super.clone();
+            return clone;
+        } catch (CloneNotSupportedException e) {
+            throw new AssertionError();
+        }
+    }
+}

core-java-modules/core-java-lang-oop-patterns/src/main/java/com/baeldung/shallowvsdeepcopy/UserWithDeepClone.java

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+package com.baeldung.shallowvsdeepcopy;
+
+public class UserWithDeepClone implements Cloneable{
+
+    private String name;
+    private Address address;
+    private int age;
+
+    public UserWithDeepClone(String name, Address address, int age) {
+        this.name = name;
+        this.address = address;
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Address getAddress() {
+        return address;
+    }
+
+    public void setAddress(Address address) {
+        this.address = address;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    @Override
+    public UserWithDeepClone clone() {
+        try {
+            UserWithDeepClone clone = (UserWithDeepClone) super.clone();
+            clone.setAddress(clone.getAddress().clone());
+            return clone;
+        } catch (CloneNotSupportedException e) {
+            throw new AssertionError();
+        }
+    }
+}

core-java-modules/core-java-lang-oop-patterns/src/main/java/com/baeldung/shallowvsdeepcopy/UserWithShallowClone.java

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+package com.baeldung.shallowvsdeepcopy;
+
+public class UserWithShallowClone implements Cloneable{
+
+    private String name;
+    private Address address;
+    private int age;
+
+    public UserWithShallowClone(String name, Address address, int age) {
+        this.name = name;
+        this.address = address;
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public void setName(String name) {
+        this.name = name;
+    }
+
+    public Address getAddress() {
+        return address;
+    }
+
+    public void setAddress(Address address) {
+        this.address = address;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    public void setAge(int age) {
+        this.age = age;
+    }
+
+    @Override
+    public UserWithShallowClone clone() {
+        try {
+            UserWithShallowClone clone = (UserWithShallowClone) super.clone();
+            return clone;
+        } catch (CloneNotSupportedException e) {
+            throw new AssertionError();
+        }
+    }
+}

core-java-modules/core-java-lang-oop-patterns/src/test/java/com/baeldung/shallowvsdeepcopy/UserCloneUnitTest.java

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+package com.baeldung.shallowvsdeepcopy;
+import org.junit.Test;
+import static org.assertj.core.api.Assertions.assertThat;
+
+public class UserCloneUnitTest {
+
+    @Test
+    public void givenUser_WhenCopyCreated_thenCopyIsShallow(){
+        Address address = new Address("abc", "444-0000", "pqr", "USA");
+        UserWithShallowClone user = new UserWithShallowClone("baeldung", address,32);
+
+        UserWithShallowClone userClone = (UserWithShallowClone)user.clone();
+        assertThat(userClone.getAddress()).isEqualTo(user.getAddress());
+    }
+
+    @Test
+    public void givenUserWithDeepCloneMethod_WhenCopyCreated_thenCopyIsDeep(){
+        Address address = new Address("abc", "444-0000", "pqr", "USA");
+        UserWithDeepClone user = new UserWithDeepClone("baeldung", address,32);
+        UserWithDeepClone userClone = (UserWithDeepClone)user.clone();
+        assertThat(userClone.getAddress()).isNotEqualTo(user.getAddress());
+    }
+}