Java – IntelliJ: Never use wildcard imports

intellij-ideajavasettings

Is there a way to tell IntelliJ never to use wildcard imports?
Under 'Settings > Code Style > Imports', I can see that you can specify the 'class count' prior to IntelliJ using wildcard imports. However, if I never want to use wildcard imports can I turn this functionality off?

I have tried putting -1 or leaving the field blank but that just tells IntelliJ to always use wildcard imports. Obviously a not-so-nice solution would be to put a ridiculously high number so that you never encounter wildcard imports but I was hoping there was a nicer way to just turn it off.

Best Answer

It's obvious why you'd want to disable this: To force IntelliJ to include each and every import individually. It makes it easier for people to figure out exactly where classes you're using come from.

Click on the Settings "wrench" icon on the toolbar, open "Imports" under "Code Style", and check the "Use single class import" selection. You can also completely remove entries under "Packages to use import with *", or specify a threshold value that only uses the "*" when the individual classes from a package exceeds that threshold.

Update: in IDEA 13 "Use single class import" does not prevent wildcard imports. The solution is to go to Preferences (⌘ + , on macOS / Ctrl + Alt + S on Windows and Linux) > Editor > Code Style > Java > Imports tab set Class count to use import with '*' and Names count to use static import with '*' to a higher value. Any value over 99 seems to work fine.

IntelliJ 14.X Onwards

From version 14.0 onwards, the path to the setting dialog is slightly different, a General submenu has been added between Editor and Appearance as shown below

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IntelliJ 8.1.2 - 13.X

From IntelliJ 8.1.2 onwards, this option is in File | Settings¹. Within the IDE Settings section of that dialog, you'll find it under Editor | Appearance.

On a Mac, these are named IntelliJ IDEA | Preferences...

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Java – a serialVersionUID and why should I use it

The docs for java.io.Serializable are probably about as good an explanation as you'll get:

The serialization runtime associates with each serializable class a version number, called a serialVersionUID, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization. If the receiver has loaded a class for the object that has a different serialVersionUID than that of the corresponding sender's class, then deserialization will result in an InvalidClassException. A serializable class can declare its own serialVersionUID explicitly by declaring a field named serialVersionUID that must be static, final, and of type long:

ANY-ACCESS-MODIFIER static final long serialVersionUID = 42L;

If a serializable class does not explicitly declare a serialVersionUID, then the serialization runtime will calculate a default serialVersionUID value for that class based on various aspects of the class, as described in the Java(TM) Object Serialization Specification. However, it is strongly recommended that all serializable classes explicitly declare serialVersionUID values, since the default serialVersionUID computation is highly sensitive to class details that may vary depending on compiler implementations, and can thus result in unexpected InvalidClassExceptions during deserialization. Therefore, to guarantee a consistent serialVersionUID value across different java compiler implementations, a serializable class must declare an explicit serialVersionUID value. It is also strongly advised that explicit serialVersionUID declarations use the private modifier where possible, since such declarations apply only to the immediately declaring class — serialVersionUID fields are not useful as inherited members.

Best Answer

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IntelliJ 14.X Onwards

IntelliJ 8.1.2 - 13.X

Java – a serialVersionUID and why should I use it

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