Question

Originally I had a java.io.File class in a jar in the classpath, which didn’t have a separatorChar property. So I ran into a problem where the following code block runs:

import java.io.File;

public class HelloWorld {

    public static void main(String[] args) { 
        System.out.println("separatorChar= " + File.separatorChar); 
    } 
}

But I changed the import statement as follows:

import java.io.*;

and then I get an error basically stating that File.separatorChar cannot be found.

What I believe is happening is import java.io.* is using a class that’s in a jar in the classpath, whereas import java.io.File is specifically using the File class that comes with Java.

The question here is why does import java.io.File work while java.io.* does not?

Answer 1

As EJP commented on the original question,

That is correct. Import java.io.* gives the compiler another place to find classes that aren’t in the current package. Import java.io.File tells the compiler which File to use. Moral: don’t reuse JDK class names.