Coming across NoClassDefFoundError in java

Question

I come across an error while running this in Java:

// Test.java
public class Test {
    public static void main(String [] args) throws IOException {
        String a = "123";
        a = a + "456";
        System.out.println(a);
    }
}

by typing in these commands:

javac Test.java
java Test

And it has reported:

Exception in thread "main" java.lang.NoClassDefFoundError: while resolving class: Test
   at java.lang.VMClassLoader.resolveClass(java.lang.Class) (/usr/lib64/libgcj.so.5.0.0)
   at java.lang.Class.initializeClass() (/usr/lib64/libgcj.so.5.0.0)
   at java.lang.Class.forName(java.lang.String, boolean, java.lang.ClassLoader) (/usr/lib64/libgcj.so.5.0.0)
   at gnu.gcj.runtime.FirstThread.run() (/usr/lib64/libgcj.so.5.0.0)
   at _Jv_ThreadRun(java.lang.Thread) (/usr/lib64/libgcj.so.5.0.0)
   at _Jv_RunMain(java.lang.Class, byte const, int, byte const, boolean) (/usr/lib64/libgcj.so.5.0.0)
   at __gcj_personality_v0 (/home/users/haotianyi/tr/java.version=1.4.2)
   at __libc_start_main (/lib64/tls/libc-2.3.4.so)
   at _Jv_RegisterClasses (/home/users/haotianyi/tr/java.version=1.4.2)
Caused by: java.lang.ClassNotFoundException: java.lang.StringBuilder not found in [file:/usr/share/java/libgcj-3.4.5.jar, file:./, core:/]
   at java.net.URLClassLoader.findClass(java.lang.String) (/usr/lib64/libgcj.so.5.0.0)
   at gnu.gcj.runtime.VMClassLoader.findClass(java.lang.String) (/usr/lib64/libgcj.so.5.0.0)
   at java.lang.ClassLoader.loadClass(java.lang.String, boolean) (/usr/lib64/libgcj.so.5.0.0)
   at _Jv_FindClass(_Jv_Utf8Const, java.lang.ClassLoader) (/usr/lib64/libgcj.so.5.0.0)
   at java.lang.Class.forName(java.lang.String, boolean, java.lang.ClassLoader) (/usr/lib64/libgcj.so.5.0.0)
   at _Jv_BytecodeVerifier.verify_instructions_0() (/usr/lib64/libgcj.so.5.0.0)
   at _Jv_VerifyMethod(_Jv_InterpMethod) (/usr/lib64/libgcj.so.5.0.0)
   at _Jv_PrepareClass(java.lang.Class) (/usr/lib64/libgcj.so.5.0.0)
   at _Jv_WaitForState(java.lang.Class, int) (/usr/lib64/libgcj.so.5.0.0)
   at java.lang.VMClassLoader.linkClass0(java.lang.Class) (/usr/lib64/libgcj.so.5.0.0)
   at java.lang.VMClassLoader.resolveClass(java.lang.Class) (/usr/lib64/libgcj.so.5.0.0)
   ...8 more

But the program runs OK when I remove the line a = a + "456";, i.e.,

// Test.java
public class Test {
    public static void main(String [] args) throws IOException {
        String a = "123";
        // a = a + "456";
        System.out.println(a);
    }
}

I wonder where is the problem and how to solve it?

http://stackoverflow.com/questions/4648607/stringbuilder-stringbuffer-vs-operator read that... and why are you running under java 1.4.2? — Tschallacka, Jun 30 '15 at 06:14
The root cause of the problem is that the JRE cannot find the `java.lang.StringBuilder` class. — Tim Biegeleisen, Jun 30 '15 at 06:15
It simply means that there is a wrong library during compilation. So probably there is a correct package but without that class/method inside. Shortly - it means that you're using wrong library/JDK — Marcin Erbel, Jun 30 '15 at 06:23
Ok, maybe there are some multiple versions of Java in my PATH... — Tianyi Hao, Jun 30 '15 at 06:27

score 5 · Accepted Answer · answered Jun 30 '15 at 06:18

The problem is that the compiler you're using is from Java 5 or later, so it's using StringBuilder instead of StringBuffer - but the execution environment you're using appears to be Java 1.4.2, which doesn't include StringBuilder.

Note that Java 1.4.2 is also ancient. I suggest you upgrade both the JDK and the JRE to a recent version (ideally straight to Java 8) - that will solve your issue and mean that you're not running on an unsupported version which may well have security bugs that haven't been patched because it's too old. (Along those lines, do you really need to use GCJ? I would stick to one of the more widely-used Java environments if you can.)

score 2 · Answer 2 · answered Jun 30 '15 at 06:19

The root cause of your error is that the JVM cannot find the java.lang.StringBuilder class. But this is ultimately a result of your using an outdated libgcj JDK instead of using a standard Sun-compliant JDK.

From the libgcj documentation:

Just look in the 'libjava' directory of libgcj and see what classes are there. Most GUI stuff isn't there yet, that's true, but many of the other classes are easy to add if they don't yet exist.

Apparently StringBuilder isn't in there, which is why you are having the problem. Make your life easy and just download Java 7 or Java 8 from the Oracle website. As @JonSkeet mentioned (and is correct as usual), you are using Java 4, which is seriously outdated.

score 1 · Answer 3 · answered Jun 30 '15 at 06:40

NoClassDefFoundError most of the time is accompanied or caused by a ClassNotFoundException so you should really look for that.

So in your stack trace you have :

Caused by: java.lang.ClassNotFoundException: java.lang.StringBuilder not found in [file:/usr/share/java/libgcj-3.4.5.jar, file:./, core:/]

That is the root cause of your exception.

You actually should never face this issue if you were to use Oracle JDK/JVM instead of GNU compiler(gcj) for Java ( Which seems to be default java in a lot of Linux's). Download Oracle JDK/JVM, install it and set that as your java command (JAVA_HOME and in PATH environment variable) and this error would go away.

Coming across NoClassDefFoundError in java

3 Answers3