Change Name of Import in Java, or import two classes with the same name

Question

In Python you can do a:

from a import b as c

How would you do this in Java, as I have two imports that are clashing.

Answer 1

There is no import aliasing mechanism in Java. You cannot import two classes with the same name and use both of them unqualified.

Import one class and use the fully qualified name for the other one, i.e.

import com.text.Formatter;

private Formatter textFormatter;
private com.json.Formatter jsonFormatter;

Answer 2

As the other answers already stated, Java does not provide this feature.

Implementation of this feature has been requested multiple times, e.g. as JDK-4194542: class name aliasing or JDK-4214789: Extend import to allow renaming of imported type.

From the comments:

This is not an unreasonable request, though hardly essential. The occasional use of fully qualified names is not an undue burden (unless the library really reuses the same simple names right and left, which is bad style).

In any event, it doesn't pass the bar of price/performance for a language change.

So I guess we will not see this feature in Java anytime soon :-P

Answer 3

It's probably worth noting that Groovy has this feature:

import java.util.Calendar
import com.example.Calendar as MyCalendar

MyCalendar myCalendar = new MyCalendar()

Answer 4

Java doesn't allow you to do that. You'll need to refer to one of the classes by its fully qualified name and only import the other one.

Answer 5

Today I filed a JEP draft to OpenJDK about this aliasing feature. I hope they will reconsider it.

If you are interested, you can find a JEP draft here: https://gist.github.com/cardil/b29a81efd64a09585076fe00e3d34de7

Answer 6

It's ridiculous that java doesn't have this yet. Scala has it

import com.text.Formatter
import com.json.{Formatter => JsonFormatter}

val Formatter textFormatter;
val JsonFormatter jsonFormatter;

Answer 7

Unless there are problems with non-default constructors you can always do this (while we all wait for the Java language specification to catch up):

public class YaddaYadda
{
    private static class ZU extends eu.zrbj.util.ZrbjUtil_3_0 { }

    public void foo (String s)
    {
        if (ZU.isNullOrEmpty(s))
        {
            // ...

For project-wide use the 'import' class can go into a separate class file, giving a single point of definition for the import.

This is a lifesaver especially with regard to 'library' classes, meaning collections of static utility functions. For one thing it gives you the ability to version these beasts - as shown in the example - without major inconvenience for the user.

Answer 8

Actually it is possible to create a shortcut so you can use shorter names in your code by doing something like this:

package com.mycompany.installer;
public abstract class ConfigurationReader {
    private static class Implementation extends com.mycompany.installer.implementation.ConfigurationReader {}
    public abstract String getLoaderVirtualClassPath();
    public static QueryServiceConfigurationReader getInstance() {
        return new Implementation();
    }
}

In that way you only need to specify the long name once, and you can have as many specially named classes you want.

Another thing I like about this pattern is that you can name the implementing class the same as the abstract base class, and just place it in a different namespace. That is unrelated to the import/renaming pattern though.