Question

I’m experiencing some strange behavior when using static imports of inherited static methods:

com/example/util/BaseUtil.java:

package com.example.util;

/*default*/ class BaseUtil {
    public static final void foo(){ System.out.println("foo"); }
}

com/example/util/Util.java:

package com.example.util;

public final class Util extends BaseUtil{
    public static void bar(){ System.out.println("bar"); }
    //foo() will be inherited
}

com/example/UtilTest.java

package com.example;

import static com.example.util.Util.bar;
import static com.example.util.Util.foo;

public class UtilTest {
    public static void main(String[] args) {
        bar();
        foo();
    }
}

Running UtilTest result in an unchecked exception!

Exception in thread "main" java.lang.IllegalAccessError: tried to access class com.example.util.BaseUtil from class com.example.UtilTest

    at com.example.UtilTest.main(UtilTest.java:15)

However, if I were to reference the methods via Util (without static imports) everything works as expected:

com/example/UtilTest.java

package com.example;

import com.example.util.Util;

public class UtilTest {
    public static void main(String[] args) {
        Util.bar();
        Util.foo();
    }
}

So, what gives?

Answer 1

/*default*/ class BaseUtil { //only visible within the package com/example/util

That class has defualt access specifier, which makes it invisible from outside of that package.

You need to make it public.

Update

Following is how the decompilation looks like:

public class com.example.UtilTest extends java.lang.Object{
public com.example.UtilTest();
  Code:
   0:   aload_0
   1:   invokespecial   #8; //Method java/lang/Object."<init>":()V
   4:   return

public static void main(java.lang.String[]);
  Code:
   0:   invokestatic    #16; //Method com/example/util/Util.bar:()V
   3:   invokestatic    #21; //Method com/example/util/BaseUtil.foo:()V
   6:   return

}

And the following is what I get by using JD GUI

package com.example;

import com.example.util.BaseUtil;
import com.example.util.Util;

public class UtilTest
{
  public static void main(String[] args)
  {
    Util.bar();
    BaseUtil.foo();
  }
}

which of course is not going to compile.

Looks like a hole in the compiler (may be due to the static imports) here.