Can a Constructor Throw an Exception in Java

Yes, constructors are allowed to throw an exception in Java.

A Constructor is a special type of a method that is used to initialize the object and it is used to create an object of a class using the new keyword, where an object is also known as an Instance of a class. Each object of a class will have its own state (Instance variables) and access to methods of its class.

Throw an Exception from a Constructor

• A checked exception can be used to indicate a legitimate problem when trying to create an instance, while an unchecked exception typically indicates a bug either in the client code or in the constructor itself.
• In both cases, an object is actually allocated in the heap space, but a reference to it is not returned. The object remains in a partially initialized state until it gets garbage collected.so we conclude that saving a reference to the object from the constructor itself (by using this reference) is a risky thing, since we may give access to an object in an invalid state.
• Another important thing to note about the exception in a constructor is related to reflection. When we need to invoke the empty constructor using a class object for example test, we sometimes use the method test.newInstance().
• Any exception thrown by the constructors is propagated without a change. In other words, the newInstance() method may throw checked exception that it does not even declare.

Example

Live Demo

public class ConstructorExceptionTest {
   public ConstructorExceptionTest() throws InterruptedException {
      System.out.println("Preparing an Object");
      Thread.sleep(1000);
      System.out.println("Object is ready");
   }
   public static void main(String args[]) {
      try {
         ConstructorExceptionTest test = new ConstructorExceptionTest();
      } catch (InterruptedException e) {
         System.out.println("Got interrupted...");
      }
   }
}

Output

Preparing an Object
Object is ready