Update README.md

Author: madhuribisht

README.md

@@ -16,4 +16,17 @@ Core Java Interview Question
    * Abstraction
    * Platform independent:** A single program works on different platforms without any modification.
    * High Performance:** JIT (Just In Time compiler) enables high performance in Java. JIT converts the bytecode into machine language and then JVM starts the execution.
-   * Multi-threaded:** A flow of execution is known as a Thread. JVM creates a thread which is called the main thread. The user can create multiple threads by extending the thread                        class or by implementing the Runnable interface.
+   * Multi-threaded:** A flow of execution is known as a Thread. JVM creates a thread which is called the main thread. The user can create multiple threads by extending the thread                        
+                       class or by implementing the Runnable interface.
+
+#### Q3  How does Java enable high performance?
+         Java uses Just In Time compiler to enable high performance. It is used to convert the instructions into bytecodes.
+ 
+#### Q4  What do you mean by Constructor?
+    #### Constructor can be explained in detail with enlisted points:
+
+       * When a new object is created in a program a constructor gets invoked corresponding to the class.
+       * The constructor is a method which has the same name as the class name.
+       * If a user doesn’t create a constructor implicitly a default constructor will be created.
+       * The constructor can be overloaded.
+       * If the user created a constructor with a parameter then he should create another constructor explicitly without a parameter.