How to resolve "unable to find package java.lang in classpath or bootclasspath" in Dr Java?

Question

I am new to Java. I am taking a University beginners Java course. I'm running my first hello world code and am getting an error message. I have installed the latest Dr. Java stable version and have installed Java SE 12 JDK.

I have uninstalled and reinstalled Dr. Java several times and still getting error message. I have also recompiled it to and still the error message is there.

public class HelloWorld {
    public static void main(String[] args) { 
        System.out.println("Hello, World");
    }
}

I expected the code output to say, "Hello World" under the interactions pane but it isn't and instead there is an error message that says, "Current document is out of sync with the Interactions Pane and should be recompiled!".

Also, under the console pane I receive the following message:

Compiler is using classPath = '[C:\Users\Admin, C:\Users\Admin\Downloads\drjava-beta-20190813-220051.jar]'; bootClassPath = 'null' Fatal Error: Unable to find package java.lang in classpath or bootclasspath

Answer 1

Realizing that the OP solved his problem by version of JDK, I ran across this question after experiencing the same symptoms he describes. With that, it seems possibly appropriate to post a solution for the symptoms even though the problem ended up not being quite "identical" to the OP's situation:

I had the same problem with compilation not working. In my case, I am using a Linux system that has both OpenJDK and a manually installed Oracle JDK (extracted from a tarball obtained from java.com), along with some other JRE environments in various places. I "installed" the DrJava Version : drjava-20190813-220051 jar file and ran it from the command-line. I then clicked [ Manual Download ] when it asked about installing updates (drjava-beta-2019-220051).

DrJava reported that my compiler was JDK 8.0_222. Note, I don't know where that compiler came from. As far as I know, I didn't have that version installed. My OpenJDK was:

$ /bin/java -version
openjdk version "1.8.0_252"
OpenJDK Runtime Environment (build 1.8.0_252-b09)
OpenJDK 64-Bit Server VM (build 25.252-b09, mixed mode)

I typed in a simple "Hello World" program, and every attempt to compile produced:

Compiler Output:
  "Compilation completed."

This is a bug, because in fact compilation apparently did not complete.

Clicking Run produced:

Interactions
  Welcome to DrJava.  Working directory is /home/krb/Projects/Software/java
  Current document is out of sync with the Interactions Pane and should be recompiled!
  > 

Restarting DrJava, saving, clicking Reset, etc., would not clear the problem.

In any event, at some point I noticed the Console tab was full of messages like:

Console
  Compiler is using classPath = '[/home/krb/Projects/Software/java, /home/apps/drjava/drjava-beta-20190813-220051.jar]';  bootClassPath = 'null'
  Fatal Error: Unable to find package java.lang in classpath or bootclasspath

At this point, I tried various things, but I focused on pointing DrJava to an Oracle Java JDK I had installed a few days ago. Everything I did was in Edit | Preferences ... | Resource Locations, though I beat around in there a while. All of the settings were "blank" before I started. Anyway, I eventually had some success after I'd set:

Web Browser
 /usr/lib64/firefox/firefox
Web Browser Command

Tools.jar Location
  /home/raid/apps/oracle/jdk-1.8.0_251/jre/lib/tools.jar
Display All Compiler Version [ ]
Extra Classpath
  /home/raid/apps/oracle/jdk1.8.0_251/jre/lib
  /home/raid/apps/oracle/jdk1.8.0_251/lib

NOTE: Your PATHs will NOT be the same as mine! You need to use the actual paths on your system. In my case I searched for "rt.jar" and "tools.jar" that were obviously in folders related to an installed JDK.

At this point I decided to try to figure out the minimum required to get it working. After a lot of fiddling around, I found it is sufficient just to set Preferences | Resource Locations | Tools.jar Location, but with with one MAJOR caveat. You must BROWSE to the file using that dialog. YOU CANNOT JUST PASTE IN THE PATH! If you just paste in the path, it can look like it is set correctly, but the compiler will continue to not work. This was how I got the oracle jdk compiler to work.

Next, I set about to see if I could get OpenJDK to work. I searched my entire system for another tools.jar that belonged to OpenJDK, and did not find one. Then I realized I did not have the DEVEL OpenJDK package installed (on Mageia Linux 7).

java-1.8.0-openjdk-headless-1.8.0.252-1.b09.1.mga7
java-1.8.0-openjdk-1.8.0.252-1.b09.1.mga7

I installed:

java-1.8.0-openjdk-devel-1.8.0.252-1.b09.1.mga7

Now, even after resetting defaults, DrJava no longer says it is using JDK 8.0_222, but rather JDK 8.0-openjdk-1.8.0.252-1.b09.1.mga7.x86_64-OpenJDK, and everything works fine with NO customization to preferences!

I don't know where the heck JDK 8.0_222 came from. There's nothing on my system with that version. I rather suppose it is some internal thing in DrJava. I think the takeaways are:

• If DrJava says its using JDK 8.0_222, it probably is not going to work!
• Make sure you actually have a tools.jar installed if your system might split up the OpenJDK installation.
• Point Tools.jar Location to an existing tools.jar file where the JDK you are using is installed, and making sure to browse to it (not just paste in a path).

I know what I saw was with Linux and a .jar install of DrJava, and this might not be what you have, but perhaps the information will be helpful in offering you things to look at and try.

Answer 2

As the answers above state, DrJava is not compatible with newer versions of Java than Java 8. Most of the DrJava codebase was written long before the open source version of Java was viable. The Sun Microsystems and Oracle javac compilers are proprietary and cannot be distributed with open source apps like DrJava. So DrJava searches for tools.jar (the library file containing the compiler in Java JDK distributions prior to Java 9) in common locations on Windows, Mac OS X, and Linux to find a compiler (more accurately, what were common locations in 2007). If you are running DrJava from a Java 8 JDK, it almost always finds it (although it appears to be failing for some installations Amazon Corretto 8). The most recent available build (March 3, 2020) of DrJava at www.cs.rice.edu/~javaplt/drjavarice may do a better job. I know it includes a later version the open source Java 8 compiler (JDK 8.0_242) and that it also finds the compiler (JDK 8.0_265) in the Corretto 8 distribution that I am using on Windows 10. The mysterious version of the open source JDK compiler reported above is being retrieved from the drjava.jar file itself. Now that the open source JDK includes a reliable compiler (which I suspect is nearly identical to the Oracle Java 8 SE compiler), the drjava.jar file includes a recent build of the open source Java 8 compiler.

Answer 3

Your solution helped me troubleshoot a problem with DrJava not recognizing the Amazon Carretta JDK on a Mac.

The fix is to open DrJava and go to Edit -> Preferences -> Resource Locations. From the Tools.jar Location box you must use the three dots at the end of that box to navigate to the tools.jar file on your Mac, which is probably in /Library/Java/JavaVirtualMachines/amazon-corretto-8.jdk/Contents/Home/lib/tools.jar.