java class initialization explanation

Question

I kind of new to java and will be happy if anybody could explain the following code samples to me.This is just a sample java code snippet for illustration. But the main question is that if the class Learn initializes another class Smart with a parameter which is also a class Object , then the addition of the dot class to the class Object Sample is kind of confusing to me. Any explanation will be appreciated. I apologize if it is a basic question. thanks.

class Learn {
//some codes 
Smart smart = new Smart(Sample.class);
//some codes
}

Keith Randall · Accepted Answer · 2012-07-30 06:21:54Z

4

Sample is the name of a class. It is not an object. A new Sample() is an object whose class is Sample. Sample.class is an object whose class is java.lang.Class which describes the class Sample.

answered Jul 30, 2012 at 6:21

Keith Randall

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2 Comments

Radu Murzea Over a year ago

Straightforward explanation without too much blabla. +1

faisal abdulai Over a year ago

thanks for the correction , but then if i may ask further how different is Sample.class from an initialization like Sample sample = new Sample()

gelu · Accepted Answer · 2012-07-30 06:40:14Z

0

In java, there is a class called "Class" that represent classes and interfaces.
There are several ways to get an instance of class "Class". Please take a look at java.lang.Class document.
- Class.forName(String className)
- obj.getClass() -obj is any class instance
- Sample.class -Sample is a class
You are using the 3rd method to get an instance of class "Sample".

answered Jul 30, 2012 at 6:40

gelu

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Comments

Kumar Vivek Mitra · Accepted Answer · 2012-07-30 06:40:19Z

0

I will break your example in the following way....

Learn - is a Class

smart - is an Object Reference Variable of type Smart, we can say that Class Learn has a reference of type Smart.

Sample.class - Is a way of getting the Class<T> for a particular type.

Extract from Java Docs.

During implementation it depends on the Targeting bytecode version. If -target 1.4 (or below), a call to Class.forName() is inserted into your code in a static method which is called during type initialization. If you use -target 1.5 (or above) the constant pool gets a "class" entry

Please refer section 15.8.2 of the Java Language Specification for more details

edited Jul 30, 2012 at 6:40

answered Jul 30, 2012 at 6:34

Kumar Vivek Mitra

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