This question already has answers here:
The difference between Classes, Objects, and Instances
(16 answers)
Closed 8 years ago.
There can only be one instance of class and can have many objects...? If not then can you please explain me difference between Instance and Object of the class
Instance and object of class are same things.
Theoratically Instance represents certain object at one time.
Example: Suppose you have Employee Class(Structure) with firstName and lastName
your instance or object(Value) represent Employee with firstname "Sanjay" and lastname "Rabari"
Related
This question already has answers here:
Why can I create an variable with type of parent class
(2 answers)
What does it mean to "program to an interface"?
(33 answers)
Closed 12 months ago.
I am currently learning Java as a past time, and I am troubling in absorbing this instantiation syntax.
I know that if a Main class is created, I can create an object by using this
Main obj = new Main();
But in further lectures (specifically inheritance and polymorphism), they are creating objects as
Parentclass object = new Subclass();
I've tried using
Subclass object = new Subclass();
and have the same output.
Can you please tell me the difference about these two?
This question already has answers here:
what is the Class object (java.lang.Class)?
(7 answers)
Closed 2 years ago.
Recently I was learning annotations in java and came across Reflection API and a part of its code was:
Meta obj = new Meta();
//Get a Class object
CLass<?> c = obj.getClass();
The thing that I am not able to understand is that what is the difference between object obj and object c since both of them are just class objects.
You could treat Class object as metadata of normal object. Moreover, when you get obj.getClass() e.g. for different Integer objects, you'll get the smae Class object.
This question already has answers here:
The difference between Classes, Objects, and Instances
(16 answers)
Closed 4 years ago.
What is the definition of a Class , Object and an Instance and what is the difference between an Instance and an Object.
I would like my answer in Simple English
Class is collection of various objects, variables, functions etc.
class DemoClass {
void method(){
......
}
}
When you want to create a new instance of a class you need to create a new object of that class.
DemoClass dc = new DemoClass();
You can then access this instance (methods etc. of this instance) from the object you created.
dc.method();
This question already has answers here:
What is a class literal in Java?
(10 answers)
Closed 5 years ago.
Where is class static field is declared and how this field is associated with every classes?
System.out.pritnln(String.class);
System.out.pritnln(Student.class);
output:
class java.lang.String
class Student
It depends on the implementation of the VM, but if you do a heap dump of the Hotspot JVM you can see a special object for each class which holds the static fields.
You can access them dynamically at runtime by using reflection.
This question already has answers here:
What does .class mean in Java?
(8 answers)
Closed 8 years ago.
What exactly is the meaning of the following construction: MyClassName.class ?
At first I thought MyClassName.class would represent the access of a static class variable defined for MyClassName class, but it that'd be true then the following assignment should be possible:
MyClassName m = new MyClassName();
Class<MyClassName> clazz = m.class; //access static class variable by using an instance variable
What is the true meaning of MyClassName.class? Is it a static class variable? is it a Java special construction?
Every class in Java has an associated instance of java.lang.Class which contains metadata about the class i.e its attributes, types, methods, super class etc.
Here MyClassName.class is called class literal. Link to Java doc for further info - http://docs.oracle.com/javase/specs/jls/se5.0/html/expressions.html#15.8.2