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
