How to use Jlex and Cup tools

Question

i'm trying to learn something about JFlex and Cup tools on Ubuntu, because i have to use them for a school project. So i downloaded and installed JFlex and Cup. There are some examples in "jflex-1.6.1/examples", so i tried to run one of them. In particularly i tried to run the one in "jflex-1.6.1/examples/cup", following the instructions in the README file:

To compile:

jflex lcalc.flex

java java_cup.Main < ycalc.cup

javac Main.java

To run:

java Main test.txt

Files:

"Main.java"       demo of a main program

"Makefile "       makefile to compile and test the example

"README"          

"lcalc.flex"      the lexer spec

"output.good "    how the output should look like for the test

"ycalc.cup"       the parser spec

"test.txt "       sample input for testing

With many difficulties, i have been finally able to compile, then to complete successfully the first three instructions. Now i have errors when i try to run: java Main test.txt. In particular i get this error:

Error: A JNI error has occurred, please check your installation and try again
Exception in thread "main" java.lang.NoClassDefFoundError: java_cup/runtime/Scanner
    at java.lang.Class.getDeclaredMethods0(Native Method)
    at java.lang.Class.privateGetDeclaredMethods(Class.java:2701)
    at java.lang.Class.privateGetMethodRecursive(Class.java:3048)
    at java.lang.Class.getMethod0(Class.java:3018)
    at java.lang.Class.getMethod(Class.java:1784)
    at sun.launcher.LauncherHelper.validateMainClass(LauncherHelper.java:544)
    at sun.launcher.LauncherHelper.checkAndLoadMain(LauncherHelper.java:526)
Caused by: java.lang.ClassNotFoundException: java_cup.runtime.Scanner
    at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
    at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:335)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 7 more

I don't have any idea on how to solve this. I tried also with other examples but the results were the same. I hope that you can help me. Thank you!

score 2 · Answer 1 · answered Dec 20 '17 at 17:34

I also got this error, and it's because I forgot to include java-cup.jar and java-cup-runtime.jar in my class path.

Try compiling like this:

javac -cp path/to/java-cup.jar Main.java

And then run your program like this:

java -cp path/to/java-cup-runtime.jar Main

How to use Jlex and Cup tools

1 Answers1