[BAEL-6623] Add code for Convert Object to String (#15000)

* Add Person class

* Add Unit tests for Person class

* Add Person class

* Add PersonWithHashCode class

* Address review comments

* Add PersonUnitTest class

* Add PersonWithHashCodeUnitTest class

* Add missing dependency

* Remove redundant code

* Remove redundant code

* Address review comments

* Address review comments

core-java-modules/core-java-string-conversions-3/pom.xml

@@ -23,4 +23,12 @@
         </resources>
     </build>
 
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.commons</groupId>
+            <artifactId>commons-lang3</artifactId>
+            <version>${commons-lang3.version}</version>
+        </dependency>
+    </dependencies>
+
 </project>

core-java-modules/core-java-string-conversions-3/src/main/java/com/baeldung/objecttostring/Person.java

@@ -0,0 +1,34 @@
+package com.baeldung.objecttostring;
+
+import org.apache.commons.lang3.builder.ToStringBuilder;
+import org.apache.commons.lang3.builder.ToStringStyle;
+
+public class Person {
+    private String name;
+    private int age;
+
+    public Person(String name, int age) {
+        this.name = name;
+        this.age = age;
+    }
+
+    public String getName() {
+        return name;
+    }
+
+    public int getAge() {
+        return age;
+    }
+
+    @Override
+    public String toString() {
+        return "Person{name='" + name + "', age=" + age + '}';
+    }
+
+    public String toCustomString() {
+        return new ToStringBuilder(this, ToStringStyle.JSON_STYLE)
+          .append("name", name)
+          .append("age", age)
+          .toString();
+    }
+}

core-java-modules/core-java-string-conversions-3/src/test/java/com/baeldung/objecttostring/PersonUnitTest.java

@@ -0,0 +1,38 @@
+package com.baeldung.objecttostring;
+
+import org.junit.Test;
+import static org.junit.Assert.assertEquals;
+
+public class PersonUnitTest {
+    @Test
+    public void givenObject_whenToString_thenConvert() {
+        Person person = new Person("Sarah", 28);
+        String expected = "Person{name='Sarah', age=28}";
+        String actual = person.toString();
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void givenObject_whenValueOf_thenConvert() {
+        Person person = new Person("Sarah", 28);
+        String expected = "Person{name='Sarah', age=28}";
+        String actual = String.valueOf(person);
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void givenObject_whenConcat_thenConvert() {
+        Person person = new Person("Sarah", 28);
+        String expected = "Person{name='Sarah', age=28}";
+        String actual = "" + person;
+        assertEquals(expected, actual);
+    }
+
+    @Test
+    public void givenObject_whenToStringBuilder_thenConvert() {
+        Person person = new Person("Sarah", 28);
+        String expected = "{\"name\":\"Sarah\",\"age\":28}";
+        String actual = person.toCustomString();
+        assertEquals(expected, actual);
+    }
+}