Import efficiency

[Crouchez]

Is importing a class directly ie.

import java.io.InputStream

more efficient than

import java.io.*;

?

What happens? Does the JVM import all the classes if using a wildcard?

 

[Stefan Ram]

more efficient than

There is run-time efficiency, memory efficiency, disk usage
efficiency ...

What happens? Does the JVM import all the classes if using a wildcard?

An import declaration allows a static member or a named type
to be referred to by a simple name that consists of a single
identifier. I don't think that the JVM is aware of it at all.

 

[Mark Rafn]

Is importing a class directly ie.

import java.io.InputStream
more efficient than
import java.io.*;

It has no effect on the generated class, so no effect on runtime efficiency.
It's probabaly a hair faster to compile.

As a developer, I prefer specific imports, as it's easy to expand a classname
if the import is there, rather than having to search through a bunch of
packages to see where SomeFooAccessor is defined.

What happens? Does the JVM import all the classes if using a wildcard?

No. The JVM doesn't see imports. They're thrown away by the compiler. The
compiler uses them to replace short type names with fully-qualified names.
There is no bytecode difference between importing specific names, wildcards,
and not importing anything in favor of using fully-qualified names everywhere.

 

[Arne Vajhøj]

An import declaration allows a static member or a named type
to be referred to by a simple name that consists of a single
identifier. I don't think that the JVM is aware of it at all.

I don't think he asked for static import just plain import.

Arne

 

[Roedy Green]

Is importing a class directly ie.

import java.io.InputStream

more efficient than

import java.io.*;

import is a purely a compile time feature. It has no effect on run
times. See http://mindprod.com/jgloss/import.html
on rules of thumb on how to use it.

 

[Lew]

I don't think he asked for static import just plain import.

The answer is the same for both domains of discourse - there is no run-time
impact.

 

[Arne Vajhøj]

The answer is the same for both domains of discourse - there is no
run-time impact.

Yep.

But maybe the original poster were a bit confused by the explanation.

Arne

 

[Crouchez]

of course it's compile time isn't it, doh

cheers for the help