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Possible Duplicate:
What are all the different ways to create an object in Java?

I came across this statement somewhere that we can create Objects in Java in 4 ways. I am familiar with two.

  1. using the new keyword
  2. using the newInstance() method

What are the other two ?

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Swayam
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    read this thread and get your annswer http://stackoverflow.com/questions/95419/what-are-all-the-different-ways-to-create-an-object-in-java – Saad May 28 '12 at 07:56
  • Not only this is a duplicate, googling "four ways to create java objects" finds multiple (essentially identical) answers right away. – NPE May 28 '12 at 07:57

3 Answers3

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According to here, you can create Java objects as follows:

  • Using new keyword This is the most common way to create an object in java. I read somewhere that almost 99% of objects are created in this way.

MyObject object = new MyObject();

  • 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();

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

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

  • 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();

npinti
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using reflection, one can call instance.forName(String className). there's also instance.clone(), tho it's debatable whether this is true initialization.

after reading on the subject, it seems there are only 3 ways to initialize an object:

The Java language has three mechanisms dedicated to ensuring proper initialization of objects: instance initializers (also called instance initialization blocks), instance variable initializers, and constructors. (Instance initializers and instance variable initializers collectively are called "initializers.") All three mechanisms result in Java code that is executed automatically when an object is created. When you allocate memory for a new object with the new operator or the newInstance() method of class Class, the Java virtual machine will insure that initialization code is run before you can use the newly-allocated memory. If you design your classes such that initializers and constructors always produce a valid state for newly-created objects, there will be no way for anyone to create and use an object that isn't properly initialized.

Reference:

Eliran Malka
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There are two newInstances:

  • reflection with Constructor: java.lang.reflect.Constructor.newInstance(Object...)
  • with Class: java.lang.Class.newInstance()
Grzegorz Grzybek
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