Related
I have a number of .java files with a number of import statements. I'd like to have Eclipse generate a tree or other view that shows for every file which other files are linked through import statements.
I've tried to google this, and most of what it gives concerns generating the AWT tree view that eclipse internally uses. Is there a view or plugin I can use to generate this import statement tree?
You are focusing on the wrong thing here. You see, import statements are mainly for human readers. You are much more concerned about the real dependencies of your classes. Who cares if a user imported class X? What you need to know is that you depend on X, and maybe also on Z, because X depends on Z.
In other words: don't spend your time parsing import statements. Use a tool such as jdeps in order to find out about the real dependencies that your classes have! Because, as said: you also need the transitive dependencies of your classes. And import statements tell you zero about these!
Given the comments by the OP: when we are really talking about "small scale", as in "I have 5 classes I want the dependencies for" then I suggest a not very nice, but efficient solution: simply remove these "other" classes. Turn to the file system, and move the classes "you depend on away". Refresh in eclipse, and make sure the errors panel gives you all errors in your project/workspace. Then start fixing them.
In other words:
when dealing with a "large" problem, then analyse class file dependencies
when working a "small" thing, then don't overthink - simply remove your dependencies and see what happens.
It is much more convenient and cleaner to use a single statement like
import java.awt.*;
than to import a bunch of individual classes
import java.awt.Panel;
import java.awt.Graphics;
import java.awt.Canvas;
...
What is wrong with using a wildcard in the import statement?
The only problem with it is that it clutters your local namespace. For example, let's say that you're writing a Swing app, and so need java.awt.Event, and are also interfacing with the company's calendaring system, which has com.mycompany.calendar.Event. If you import both using the wildcard method, one of these three things happens:
You have an outright naming conflict between java.awt.Event and com.mycompany.calendar.Event, and so you can't even compile.
You actually manage only to import one (only one of your two imports does .*), but it's the wrong one, and you struggle to figure out why your code is claiming the type is wrong.
When you compile your code, there is no com.mycompany.calendar.Event, but when they later add one, your previously valid code suddenly stops compiling.
The advantage of explicitly listing all imports is that I can tell at a glance which class you meant to use, which simply makes reading the code much easier. If you're just doing a quick one-off thing, there's nothing explicitly wrong, but future maintainers will thank you for your clarity otherwise.
Here's a vote for star imports. An import statement is intended to import a package, not a class. It is much cleaner to import entire packages; the issues identified here (e.g. java.sql.Date vs java.util.Date) are easily remedied by other means, not really addressed by specific imports and certainly do not justify insanely pedantic imports on all classes. There is nothing more disconcerting than opening a source file and having to page through 100 import statements.
Doing specific imports makes refactoring more difficult; if you remove/rename a class, you need to remove all of its specific imports. If you switch an implementation to a different class in the same package, you have to go fix the imports. While these extra steps can be automated, they are really productivity hits for no real gain.
If Eclipse didn't do specific class imports by default, everyone would still be doing star imports. I'm sorry, but there's really no rational justification for doing specific imports.
Here's how to deal with class conflicts:
import java.sql.*;
import java.util.*;
import java.sql.Date;
Please see my article Import on Demand is Evil
In short, the biggest problem is that your code can break when a class is added to a package you import. For example:
import java.awt.*;
import java.util.*;
// ...
List list;
In Java 1.1, this was fine; List was found in java.awt and there was no conflict.
Now suppose you check in your perfectly working code, and a year later someone else brings it out to edit it, and is using Java 1.2.
Java 1.2 added an interface named List to java.util. BOOM! Conflict. The perfectly working code no longer works.
This is an EVIL language feature. There is NO reason that code should stop compiling just because a type is added to a package...
In addition, it makes it difficult for a reader to determine which "Foo" you're using.
It's not bad to use a wild card with a Java import statement.
In Clean Code, Robert C. Martin actually recommends using them to avoid long import lists.
Here is the recommendation:
J1: Avoid Long Import Lists by Using
Wildcards
If you use two or more classes from a
package, then import the whole package
with
import package.*;
Long lists of imports are daunting to
the reader. We don’t want to clutter
up the tops of our modules with 80
lines of imports. Rather we want the
imports to be a concise statement
about which packages we collaborate
with.
Specific imports are hard
dependencies, whereas wildcard imports
are not. If you specifically import a
class, then that class must exist. But
if you import a package with a
wildcard, no particular classes need
to exist. The import statement simply
adds the package to the search path
when hunting for names. So no true
dependency is created by such imports,
and they therefore serve to keep our
modules less coupled.
There are times when the long list of
specific imports can be useful. For
example, if you are dealing with
legacy code and you want to find out
what classes you need to build mocks
and stubs for, you can walk down the
list of specific imports to find out
the true qualified names of all those
classes and then put the appropriate
stubs in place. However, this use for
specific imports is very rare.
Furthermore, most modern IDEs will
allow you to convert the wildcarded
imports to a list of specific imports
with a single command. So even in the
legacy case it’s better to import
wildcards.
Wildcard imports can sometimes cause
name conflicts and ambiguities. Two
classes with the same name, but in
different packages, will need to be
specifically imported, or at least
specifically qualified when used. This
can be a nuisance but is rare enough
that using wildcard imports is still
generally better than specific
imports.
Performance: No impact on performance as byte code is same.
though it will lead to some compile overheads.
Compilation: on my personal machine, Compiling a blank class without importing anything takes 100 ms but same class when import java.* takes 170 ms.
It clutters your namespace, requiring you to fully specify any classnames that are ambiguous. The most common occurence of this is with:
import java.util.*;
import java.awt.*;
...
List blah; // Ambiguous, needs to be qualified.
It also helps make your dependencies concrete, as all of your dependencies are listed at the top of the file.
It helps to identify classname conflicts: two classes in different packages that have the same name. This can be masked with the * import.
It makes dependencies explicit, so that anyone who has to read your code later knows what you meant to import and what you didn't mean to import.
It can make some compilation faster because the compiler doesn't have to search the whole package to identify depdencies, though this is usually not a huge deal with modern compilers.
The inconvenient aspects of explicit imports are minimized with modern IDEs. Most IDEs allow you to collapse the import section so it's not in the way, automatically populate imports when needed, and automatically identify unused imports to help clean them up.
Most places I've worked that use any significant amount of Java make explicit imports part of the coding standard. I sometimes still use * for quick prototyping and then expand the import lists (some IDEs will do this for you as well) when productizing the code.
I prefer specific imports, because it allows me to see all the external references used in the file without looking at the whole file. (Yes, I know it won't necessarily show fully qualified references. But I avoid them whenever possible.)
In a previous project I found that changing from *-imports to specific imports reduced compilation time by half (from about 10 minutes to about 5 minutes). The *-import makes the compiler search each of the packages listed for a class matching the one you used. While this time can be small, it adds up for large projects.
A side affect of the *-import was that developers would copy and paste common import lines rather than think about what they needed.
In DDD book
In whatever development technology the implementation will be based on, look for ways of minimizing the
work of refactoring MODULES . In Java, there is no escape from importing into individual classes, but you
can at least import entire packages at a time, reflecting the intention that packages are highly cohesive units
while simultaneously reducing the effort of changing package names.
And if it clutters local namespace its not your fault - blame the size of the package.
Here are the few things that I found regarding this topic.
During compilation, the compiler tries to find classes that are used in the code from the .* import and the corresponding byte code will be generated by selecting the used classes from .* import. So the byte code of using .* import or .class names import will be same and the runtime performance will also be the same because of the same byte code.
In each compilation, the compiler has to scan all the classes of .* package to match the classes that are actually used in the code. So, code with .* import takes more time during the compilation process as compared to using .class name imports.
Using .* import helps to make code more cleaner
Using .* import can create ambiguity when we use two classes of the same name from two different packages. Eg, Date is available in both packages.
import java.util.*;
import java.sql.*;
public class DateDemo {
private Date utilDate;
private Date sqlDate;
}
The most important one is that importing java.awt.* can make your program incompatible with a future Java version:
Suppose that you have a class named "ABC", you're using JDK 8 and you import java.util.*. Now, suppose that Java 9 comes out, and it has a new class in package java.util that by coincidence also happens to be called "ABC". Your program now will not compile on Java 9, because the compiler doesn't know if with the name "ABC" you mean your own class or the new class in java.awt.
You won't have that problem when you import only those classes explicitly from java.awt that you actually use.
Resources:
Java Imports
Among all the valid points made on both sides I haven't found my main reason to avoid the wildcard: I like to be able to read the code and know directly what every class is, or if it's definition isn't in the language or the file, where to find it. If more than one package is imported with * I have to go search every one of them to find a class I don't recognize. Readability is supreme, and I agree code should not require an IDE for reading it.
For the record:
When you add an import, you are also indicating your dependencies.
You could see quickly what are the dependencies of files (excluding classes of the same namespace).
There is no runtime impact, as compiler automatically replaces the * with concrete class names. If you decompile the .class file, you would never see import ...*.
C# always uses * (implicitly) as you can only using package name. You can never specify the class name at all. Java introduces the feature after c#. (Java is so tricky in many aspects but it's beyond this topic).
In Intellij Idea when you do "organize imports", it automatically replaces multiple imports of the same package with *. This is a mandantory feature as you can not turn it off (though you can increase the threshold).
The case listed by the accepted reply is not valid. Without * you still got the same issue. You need specify the pakcage name in your code no matter you use * or not.
Forget about cluttered namespaces... And consider the poor soul who has to read and understand your code on GitHub, in vi, Notepad++, or some other non-IDE text editor.
That person has to painstakingly look up every token that comes from one of the wildcards against all the classes and references in each wildcarded scope... just to figure out what in the heck is going on.
If you're writing code for the compiler only - and you know what you're doing - I'm sure there's no problem with wildcards.
But if other people - including future you - want to quickly make sense of a particular code file on one reading, then explicit references help a lot.
Why is using a wild card with a Java import statement bad?
If you're using an IDE (which you should be doing), and there are more code owners than just you, using wildcard imports is bad because it:
conceals information from the rest of the team
provides only false benefits (things which are better-solved using IDE functionality than with wildcard imports) to you as an individual
Most of the "use wildcards" proponents have a focus on the individual: I don't want to maintain the list, I don't want see the clutter, etc. Here are several of the common examples:
maintenance is harder – when you want to introduce a new class into your source code, you have to manually add the import statement
refactoring is more difficult – if code is moved around, then import statements have to be updated
reduce clutter, tidy up file contents – goal here is something along the lines of "removing distractions"
These arguments were more convincing before IDEs did all of that automatically. If you're using a plain text editor instead of an IDE, then these arguments have some merit. But if you're using a plain text editor, you are already subjecting yourself to a number of other much more significant inefficiencies, and managing import statements is just one among many things that you should stop doing by hand. IDEs offer automatic management of imports, powerful refactoring tools, and folding (hiding) of any parts of the code you don't want to see.
For the "avoid wildcards" proponents, there are many examples, but I'll point out only one:
clarity – specifically, when someone new enters the codebase. They will arrive with questions, and continue to discover new questions as they explore the code. For this new code contributor, wildcard import statements do not answer any questions, and at worst can produce confusion, misunderstanding, new questions. In contrast, with explicit imports (and using an IDE) the worst case is neutral: no new info provided; at best, it not only reduces ambiguity but it can also provide answers.
At the end of the day, it helps the entire team to reduce (albeit in a small way) code complexity, to reduce confusion, to add clarity.
Importing all the classes in a package is considered a blind approach. A major reason for this is that it clutters the class namespace and could lead to conflicts between classes in different packages with the same name.
Specifically populating the necessary classes avoids that problem and clearly shows which versions were wanted. This is good for code maintainability.
I've been working on an Android app in Eclipse, and it's gradually grown in complexity to the point where I find it difficult to locate individual classes in the Package explorer.
Java isn't my strong point, I come from a Visual Studio/C Sharp background, so my first thought was to move logical groups of classes into new packages, a bit like creating a new code folder in Visual Studio.
I created a new package, com.mycompany.myapp.activities and dragged all the Activity.java files into here.
The whole thing went pretty badly, I got tons of import errors, resources failed to build, and so on. The auto refactor tool messed up my Manifest file pretty badly too. It just doesn't seem like it was designed to work that way - I ended up moving them all back, and wasted two hours fixing it.
So my question is, does Eclipse have some way to organise .java files into logical subfolders without having to create new packages for them? I'd like to make a folder for 'Data Model', one for 'Activities', one for 'Interfaces' and so on.
How would I go about doing this? Or am I thinking about this the wrong way?
So my question is, does Eclipse have some way to organise .java files into logical subfolders without having to create new packages for them?
AFAIK, no. You just need to fix up stuff related to moving your code into packages.
I got tons of import errors
Your app's R.java is generated into your application package (com.mycompany.myapp), and any classes in that same package get R via auto-import. Code residing in other packages needs to import that class (e.g., import com.mycompany.myapp.R). Hence, if you refactor a class from your app's package to a sub-package, you need to add the import.
resources failed to build
That seems unlikely, as resources know nothing about Java packages. However, without any details, it is difficult to provide you with concrete assistance.
The auto refactor tool messed up my Manifest file pretty badly too
You would need to adjust your <activity> elements to ensure they point to the newly-repackaged classes. Ditto for any other components that you repackage (e.g., services). Beyond that, without any details, it is difficult to provide you with concrete assistance.
It just doesn't seem like it was designed to work that way
Certainly, moving activities into other packages is supported. Whether the ADT plugin handles all aspects of it with aplomb is another issue. If you come up with concrete repeatable scenarios where the ADT plugin is not doing the right thing, file an issue at http://b.android.com.
I wrote a package in eclipse (Java/Android package, that is). Now I want to make another package which is a slight variation on the original. My plan is to copy and paste each .java file into the new package and change the import package.somename to the name of the new package, and develop from there. Is there a better way to do this?
Select the package in the project explorer, press Ctrl+C and then Ctrl+V, Eclipse will prompt with a package name conflict warning and ask you to enter a new package name. Just enter it and Eclipse will repackage all copied classes accordingly.
Unrelated to the problem, there's a design smell in your approach :)
In a comment on an answer you've given the reason you want to do this: "Now I want to put up a free demo version, with some functionality removed."
Instead of copying all the code to another package I'd take the approach of having only one code base and using a build parameter to specify if you're building the free or commercial version. The classes and config (e.g. spring) that are included in the build could then depend on this parameter.
Duplicating the codebase may seem like the easier option now but will duplicate your work in the long run when maintaining it, and increase the risk of bugs.
How about just extend the classes you want to change? that way you can the two variations in the same package
Depending on how much "slight variation" really is you might want to keep it as one package and handle the differences. Reasons you might not want to do this is that by duplicating a whole package for only small changes is not really clean. Duplicated code is a code smell and can cause headaches in the future if a bug is found in one package and needs to be fixed as well in other sections of code.
To answer the question though, Eclipse should have the functionality to copy the whole package and to paste it back into the project. You will have to rename either one of the packages so that you have a unique package name though.
It is much more convenient and cleaner to use a single statement like
import java.awt.*;
than to import a bunch of individual classes
import java.awt.Panel;
import java.awt.Graphics;
import java.awt.Canvas;
...
What is wrong with using a wildcard in the import statement?
The only problem with it is that it clutters your local namespace. For example, let's say that you're writing a Swing app, and so need java.awt.Event, and are also interfacing with the company's calendaring system, which has com.mycompany.calendar.Event. If you import both using the wildcard method, one of these three things happens:
You have an outright naming conflict between java.awt.Event and com.mycompany.calendar.Event, and so you can't even compile.
You actually manage only to import one (only one of your two imports does .*), but it's the wrong one, and you struggle to figure out why your code is claiming the type is wrong.
When you compile your code, there is no com.mycompany.calendar.Event, but when they later add one, your previously valid code suddenly stops compiling.
The advantage of explicitly listing all imports is that I can tell at a glance which class you meant to use, which simply makes reading the code much easier. If you're just doing a quick one-off thing, there's nothing explicitly wrong, but future maintainers will thank you for your clarity otherwise.
Here's a vote for star imports. An import statement is intended to import a package, not a class. It is much cleaner to import entire packages; the issues identified here (e.g. java.sql.Date vs java.util.Date) are easily remedied by other means, not really addressed by specific imports and certainly do not justify insanely pedantic imports on all classes. There is nothing more disconcerting than opening a source file and having to page through 100 import statements.
Doing specific imports makes refactoring more difficult; if you remove/rename a class, you need to remove all of its specific imports. If you switch an implementation to a different class in the same package, you have to go fix the imports. While these extra steps can be automated, they are really productivity hits for no real gain.
If Eclipse didn't do specific class imports by default, everyone would still be doing star imports. I'm sorry, but there's really no rational justification for doing specific imports.
Here's how to deal with class conflicts:
import java.sql.*;
import java.util.*;
import java.sql.Date;
Please see my article Import on Demand is Evil
In short, the biggest problem is that your code can break when a class is added to a package you import. For example:
import java.awt.*;
import java.util.*;
// ...
List list;
In Java 1.1, this was fine; List was found in java.awt and there was no conflict.
Now suppose you check in your perfectly working code, and a year later someone else brings it out to edit it, and is using Java 1.2.
Java 1.2 added an interface named List to java.util. BOOM! Conflict. The perfectly working code no longer works.
This is an EVIL language feature. There is NO reason that code should stop compiling just because a type is added to a package...
In addition, it makes it difficult for a reader to determine which "Foo" you're using.
It's not bad to use a wild card with a Java import statement.
In Clean Code, Robert C. Martin actually recommends using them to avoid long import lists.
Here is the recommendation:
J1: Avoid Long Import Lists by Using
Wildcards
If you use two or more classes from a
package, then import the whole package
with
import package.*;
Long lists of imports are daunting to
the reader. We don’t want to clutter
up the tops of our modules with 80
lines of imports. Rather we want the
imports to be a concise statement
about which packages we collaborate
with.
Specific imports are hard
dependencies, whereas wildcard imports
are not. If you specifically import a
class, then that class must exist. But
if you import a package with a
wildcard, no particular classes need
to exist. The import statement simply
adds the package to the search path
when hunting for names. So no true
dependency is created by such imports,
and they therefore serve to keep our
modules less coupled.
There are times when the long list of
specific imports can be useful. For
example, if you are dealing with
legacy code and you want to find out
what classes you need to build mocks
and stubs for, you can walk down the
list of specific imports to find out
the true qualified names of all those
classes and then put the appropriate
stubs in place. However, this use for
specific imports is very rare.
Furthermore, most modern IDEs will
allow you to convert the wildcarded
imports to a list of specific imports
with a single command. So even in the
legacy case it’s better to import
wildcards.
Wildcard imports can sometimes cause
name conflicts and ambiguities. Two
classes with the same name, but in
different packages, will need to be
specifically imported, or at least
specifically qualified when used. This
can be a nuisance but is rare enough
that using wildcard imports is still
generally better than specific
imports.
Performance: No impact on performance as byte code is same.
though it will lead to some compile overheads.
Compilation: on my personal machine, Compiling a blank class without importing anything takes 100 ms but same class when import java.* takes 170 ms.
It clutters your namespace, requiring you to fully specify any classnames that are ambiguous. The most common occurence of this is with:
import java.util.*;
import java.awt.*;
...
List blah; // Ambiguous, needs to be qualified.
It also helps make your dependencies concrete, as all of your dependencies are listed at the top of the file.
It helps to identify classname conflicts: two classes in different packages that have the same name. This can be masked with the * import.
It makes dependencies explicit, so that anyone who has to read your code later knows what you meant to import and what you didn't mean to import.
It can make some compilation faster because the compiler doesn't have to search the whole package to identify depdencies, though this is usually not a huge deal with modern compilers.
The inconvenient aspects of explicit imports are minimized with modern IDEs. Most IDEs allow you to collapse the import section so it's not in the way, automatically populate imports when needed, and automatically identify unused imports to help clean them up.
Most places I've worked that use any significant amount of Java make explicit imports part of the coding standard. I sometimes still use * for quick prototyping and then expand the import lists (some IDEs will do this for you as well) when productizing the code.
I prefer specific imports, because it allows me to see all the external references used in the file without looking at the whole file. (Yes, I know it won't necessarily show fully qualified references. But I avoid them whenever possible.)
In a previous project I found that changing from *-imports to specific imports reduced compilation time by half (from about 10 minutes to about 5 minutes). The *-import makes the compiler search each of the packages listed for a class matching the one you used. While this time can be small, it adds up for large projects.
A side affect of the *-import was that developers would copy and paste common import lines rather than think about what they needed.
In DDD book
In whatever development technology the implementation will be based on, look for ways of minimizing the
work of refactoring MODULES . In Java, there is no escape from importing into individual classes, but you
can at least import entire packages at a time, reflecting the intention that packages are highly cohesive units
while simultaneously reducing the effort of changing package names.
And if it clutters local namespace its not your fault - blame the size of the package.
Here are the few things that I found regarding this topic.
During compilation, the compiler tries to find classes that are used in the code from the .* import and the corresponding byte code will be generated by selecting the used classes from .* import. So the byte code of using .* import or .class names import will be same and the runtime performance will also be the same because of the same byte code.
In each compilation, the compiler has to scan all the classes of .* package to match the classes that are actually used in the code. So, code with .* import takes more time during the compilation process as compared to using .class name imports.
Using .* import helps to make code more cleaner
Using .* import can create ambiguity when we use two classes of the same name from two different packages. Eg, Date is available in both packages.
import java.util.*;
import java.sql.*;
public class DateDemo {
private Date utilDate;
private Date sqlDate;
}
The most important one is that importing java.awt.* can make your program incompatible with a future Java version:
Suppose that you have a class named "ABC", you're using JDK 8 and you import java.util.*. Now, suppose that Java 9 comes out, and it has a new class in package java.util that by coincidence also happens to be called "ABC". Your program now will not compile on Java 9, because the compiler doesn't know if with the name "ABC" you mean your own class or the new class in java.awt.
You won't have that problem when you import only those classes explicitly from java.awt that you actually use.
Resources:
Java Imports
Among all the valid points made on both sides I haven't found my main reason to avoid the wildcard: I like to be able to read the code and know directly what every class is, or if it's definition isn't in the language or the file, where to find it. If more than one package is imported with * I have to go search every one of them to find a class I don't recognize. Readability is supreme, and I agree code should not require an IDE for reading it.
For the record:
When you add an import, you are also indicating your dependencies.
You could see quickly what are the dependencies of files (excluding classes of the same namespace).
There is no runtime impact, as compiler automatically replaces the * with concrete class names. If you decompile the .class file, you would never see import ...*.
C# always uses * (implicitly) as you can only using package name. You can never specify the class name at all. Java introduces the feature after c#. (Java is so tricky in many aspects but it's beyond this topic).
In Intellij Idea when you do "organize imports", it automatically replaces multiple imports of the same package with *. This is a mandantory feature as you can not turn it off (though you can increase the threshold).
The case listed by the accepted reply is not valid. Without * you still got the same issue. You need specify the pakcage name in your code no matter you use * or not.
Forget about cluttered namespaces... And consider the poor soul who has to read and understand your code on GitHub, in vi, Notepad++, or some other non-IDE text editor.
That person has to painstakingly look up every token that comes from one of the wildcards against all the classes and references in each wildcarded scope... just to figure out what in the heck is going on.
If you're writing code for the compiler only - and you know what you're doing - I'm sure there's no problem with wildcards.
But if other people - including future you - want to quickly make sense of a particular code file on one reading, then explicit references help a lot.
Why is using a wild card with a Java import statement bad?
If you're using an IDE (which you should be doing), and there are more code owners than just you, using wildcard imports is bad because it:
conceals information from the rest of the team
provides only false benefits (things which are better-solved using IDE functionality than with wildcard imports) to you as an individual
Most of the "use wildcards" proponents have a focus on the individual: I don't want to maintain the list, I don't want see the clutter, etc. Here are several of the common examples:
maintenance is harder – when you want to introduce a new class into your source code, you have to manually add the import statement
refactoring is more difficult – if code is moved around, then import statements have to be updated
reduce clutter, tidy up file contents – goal here is something along the lines of "removing distractions"
These arguments were more convincing before IDEs did all of that automatically. If you're using a plain text editor instead of an IDE, then these arguments have some merit. But if you're using a plain text editor, you are already subjecting yourself to a number of other much more significant inefficiencies, and managing import statements is just one among many things that you should stop doing by hand. IDEs offer automatic management of imports, powerful refactoring tools, and folding (hiding) of any parts of the code you don't want to see.
For the "avoid wildcards" proponents, there are many examples, but I'll point out only one:
clarity – specifically, when someone new enters the codebase. They will arrive with questions, and continue to discover new questions as they explore the code. For this new code contributor, wildcard import statements do not answer any questions, and at worst can produce confusion, misunderstanding, new questions. In contrast, with explicit imports (and using an IDE) the worst case is neutral: no new info provided; at best, it not only reduces ambiguity but it can also provide answers.
At the end of the day, it helps the entire team to reduce (albeit in a small way) code complexity, to reduce confusion, to add clarity.
Importing all the classes in a package is considered a blind approach. A major reason for this is that it clutters the class namespace and could lead to conflicts between classes in different packages with the same name.
Specifically populating the necessary classes avoids that problem and clearly shows which versions were wanted. This is good for code maintainability.