Static Imports

[Abhi vijay]

When

   import static java.lang.Integer.*; 

This means all the static members of Integer class will be imported.

   import static java.lang.Integer; 

What does this mean?

[Punit Singh]

That is wrong syntax, it means import Integer class statically that is not possible.

[Abhi vijay]

  import static java.io.*;  

is this an incorrect import?

[Punit Singh]

Abhi vijay wrote:

  import static java.io.*;  

is this an incorrect import?

Yes, as outer class cannot be declared static ever.
Tell me your thinking over this, then I will be able to tell you more.

[Punit Singh]

public class OuterClass1{
	public static class InnerClass1{}
}

Then you can use this import statement in other classes to use InnerClass1.

import static OuterClass1.InnerClass1;

[Abhi vijay]

Punit, in devaka Cooray's Simulator, I read you cannot import an entire class.
i.e import static java.io.*; is not correct

[Punit Singh]

Abhi vijay wrote:Punit, in devaka Cooray's Simulator, I read you cannot import an entire class.
i.e import static java.io.*; is not correct

Yes I know this is not correct, I told you the reason behind that is static outer class is not possible.

Think this way, static keyword is there for just import static things, not non-static things.

[Abhi vijay]

so,
import static java.io.BufferedReader.*; is correct?

[Punit Singh]

Abhi vijay wrote:so,
import static java.io.BufferedReader.*; is correct?

Yes it is correct, now you tell me why and also what will be imported by this line?

[Abhi vijay]

io is the outer class, so it cannot be static.
It will import all static members of BufferedReader.
Right,Sir?

[Punit Singh]

Abhi vijay wrote:io is the outer class, so it cannot be static.
It will import all static members of BufferedReader.
Right,Sir?

Wrong student, io is not a class. Now search and tell me what is io?

[Abhi vijay]

oops......I mean package.

[Punit Singh]

Abhi vijay wrote:oops......I mean package.

So now tell me what is the meaning of

import static java.io.*; 

?

[Abhi vijay]

Import all the static members(classes) of IO package.

[Punit Singh]

Abhi vijay wrote:Import all the static members(classes) of IO package.

That's why it is wrong.

[Abhi vijay]

Got it, Sir

[Punit Singh]

Abhi vijay wrote:Got it, Sir

Great Grasshoper

[Abhi vijay]

1 more doubt, Punit

import java.io.BufferedReader.*;
Is this fine?

[Punit Singh]

Abhi vijay wrote:1 more doubt, Punit

import java.io.BufferedReader.*;
Is this fine?

Ya, it is importing all non-static public methods, members, inner classes of the BufferedReader class.

[Sachin Adat]

Punit Singh wrote:Ya, it is importing all non-static public methods, members, inner classes of the BufferedReader class.

How? How can you use these methods, members, innerclasses of the BufferedReader class without an instance?
I thought import is only for classes, either a single class or all classes in a package.
I've never seen anything where import is class.*;
I see that it does not give any error. But what is the use?
Can someone explain with example?

[Punit Singh]

Sachin Adat wrote:

Punit Singh wrote:Ya, it is importing all non-static public methods, members, inner classes of the BufferedReader class.

How? How can you use these methods, members, innerclasses of the BufferedReader class without an instance?
I thought import is only for classes, either a single class or all classes in a package.
I've never seen anything where import is class.*;
I see that it does not give any error. But what is the use?
Can someone explain with example?

Yes, you are right Sachin, it is just a valid syntax, but of no use.

[Ankit Garg]

Punit Singh wrote:Yes, you are right Sachin, it is just a valid syntax, but of no use.

Nope! It has a use. It is used to import static and non-static inner classes. Look at this example

myApp/Try.java

package myApp;

public class Try
{
	public class Inner{}
	public static class StaticInner{}
}

ImportExp.java

import myApp.Try.*;

class ImportExp
{
	public static void main(String[] args)
	{
		Inner obj = new myApp.Try().new Inner();
		StaticInner obj1 = new StaticInner();
	}
}

Now if you remove the import, then there will be error that cannot find symbol Inner and StaticInner ...

[Punit Singh]

Good Ankit, It seems my battery is bit down today.

[Sachin Adat]

Nice explanation Ankit and a good example too.......

[Piyush Porwal]

Ankit Garg wrote:remove the import, then there will be error that cannot find symbol Inner and StaticInner ...

Actually if you use

import myApp.Try.*;

it is called bad programming (from what I have been taught). You should always specify each and every class/member you want to import so that it will be clear when what is the dependency (quite useful while maintaining the code).

You should say:

import myApp.Try.Inner;
import myApp.Try.StaticInner;

[Punit Singh]

Ok Guruji.

[Ankit Garg]

Piyush Porwal wrote:Actually if you use

import myApp.Try.*;

it is called bad programming

Did I say that it is good programming?? I was just saying that it is legal and it has a use as opposed to what punit said. I know that importing using * like import java.io.* etc is bad programming practice

[Sachin Adat]

Piyush Porwal wrote: it is called bad programming (from what I have been taught).

Hi Piyush, thanks for your inputs. You maybe right, but the point here was about the use (ie. how to use the imports) and not about good programming.
Anyways, thanks for your reply too, even that helped(especially knowing about good programming).

[Piyush Porwal]

No offense to your effort Ankit, I wanted to add more colors to what you mentioned.

[Ankit Garg]

Piyush Porwal wrote:No offense to your effort Ankit, I wanted to add more colors to what you mentioned.

Hey don't worry. I also didn't meant anything bad. But after writing what I wrote, I thought that it looks harsh so I added an emoticon in the end to show what was my expression when I was writing the response