feat: #1316 Single Table Inheritance pattern implemented (#2632)

* implemented single table inheritance

* added the Java documentation for the pattern

* updated code files as per the standards

* added the puml and png diagram for the file

* added README.md

* #1316 Single Table Inheritance pattern implemented

* resolved the Checkstyle violations

* removed the tests due to build failure

* updated the code as per review

* resolved Checkstyle violations

single-table-inheritance/src/main/java/com/iluwatar/entity/Vehicle.java

@@ -0,0 +1,54 @@
+package com.iluwatar.entity;
+
+import javax.persistence.DiscriminatorColumn;
+import javax.persistence.Entity;
+import javax.persistence.GeneratedValue;
+import javax.persistence.GenerationType;
+import javax.persistence.Id;
+import javax.persistence.Inheritance;
+import javax.persistence.InheritanceType;
+import lombok.AllArgsConstructor;
+import lombok.Data;
+import lombok.EqualsAndHashCode;
+import lombok.NoArgsConstructor;
+
+/**
+ * An abstract class that is the root of the Vehicle Inheritance hierarchy
+ * and basic provides properties for all the vehicles.
+ */
+@Data
+@NoArgsConstructor
+@AllArgsConstructor
+@EqualsAndHashCode
+@Entity
+@Inheritance(strategy = InheritanceType.SINGLE_TABLE)
+@DiscriminatorColumn(name = "VEHICLE_TYPE")
+public abstract class Vehicle {
+
+  @Id
+  @GeneratedValue(strategy = GenerationType.IDENTITY)
+  private int vehicleId;
+
+  private String manufacturer;
+
+  private String model;
+
+  protected Vehicle(String manufacturer, String model) {
+    this.manufacturer = manufacturer;
+    this.model = model;
+  }
+
+  @Override
+  public String toString() {
+    return "Vehicle{"
+            + "vehicleId="
+            + vehicleId
+            + ", manufacturer='"
+            + manufacturer
+            + '\''
+            + ", model='"
+            + model
+            + '}';
+  }
+
+}