What are all the different ways to create an object in Java

Question

There's the obvious which is to use a constructor, but what other ways are there?

Answer 1

There are four different ways to create objects in java:

A. Using new keyword
This is the most common way to create an object in java. Almost 99% of objects are created in this way.

 MyObject object = new MyObject();

B. Using Class.forName()
If we know the name of the class & if it has a public default constructor we can create an object in this way.

MyObject object = (MyObject) Class.forName("subin.rnd.MyObject").newInstance();

C. Using clone()
The clone() can be used to create a copy of an existing object.

MyObject anotherObject = new MyObject();
MyObject object = (MyObject) anotherObject.clone();

D. Using object deserialization
Object deserialization is nothing but creating an object from its serialized form.

ObjectInputStream inStream = new ObjectInputStream(anInputStream );
MyObject object = (MyObject) inStream.readObject();

Hope this helps!

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Thanks!

Answer 2

There are different ways you could do this :

• Using Class.newInstance.

• Using Constructor.newInstance.

• Using deserialisation (uses the no-args constructor of the most derived non-serialisable base class).

• Using Object.clone (does not call a constructor).

• Using JNI (should call a constructor).

• Through any other method that calls a new.

• You could describe class loading as creating new objects (such as interned Strings).

• A literal array as part of the initialisation in a declaration (no constructor for arrays).

• The array in a "varargs" (...) method call (no constructor for arrays).

• Non-compile time constant string concatenation (happens to produce at least four objects, on a typical implementation).

• Causing an exception to be created and thrown by the runtime. For instance throw null;or "".toCharArray()[0].

• Oh, and boxing of primitives (unless cached), of course.

• JDK8 should have lambdas (essentially concise anonymous inner classes), which are implicitly converted to objects.

• There's some syntax with the new keyword also.