Does Java have a limit on the class name length?

Question

This question came up in Spring class, which has some rather long class names. Is there a limit in the language for class name lengths?

score 51 · Accepted Answer · edited Apr 17 '12 at 16:55

51

The Java Language Specification states that identifiers are unlimited in length.

In practice though, the filesystem will limit the length of the resulting file name.

edited Apr 17 '12 at 16:55

chepseskaf

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answered Jun 24 '09 at 15:18

Robert Munteanu

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The Java VM Specification states that any constant string is restricted to 65535 bytes: http://java.sun.com/docs/books/jvms/second_edition/html/ClassFile.doc.html#88659 – user85421 Nov 27 '09 at 22:15
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This is from the second edition ( same as Jon's answer ) . There is no such reference in the third edition. – Robert Munteanu Nov 29 '09 at 21:42
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current link is broken – Lambart Jan 19 '16 at 18:32

score 33 · Answer 2 · edited Nov 03 '19 at 07:17

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65535 characters I believe. From the Java virtual machine specification:

The length of field and method names, field and method descriptors, and other constant string values is limited to 65535 characters by the 16-bit unsigned length item of the CONSTANT_Utf8_info structure (§4.4.7). Note that the limit is on the number of bytes in the encoding and not on the number of encoded characters. UTF-8 encodes some characters using two or three bytes. Thus, strings incorporating multibyte characters are further constrained.

here:

https://docs.oracle.com/javase/specs/jvms/se6/html/ClassFile.doc.html#88659

edited Nov 03 '19 at 07:17

valiano

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answered Jun 24 '09 at 15:21

Jon

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Do you have a such a reference for the third edition? I'm unable to find one. – Robert Munteanu Jun 24 '09 at 15:24
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65535 is a limitation of the JVM not the language itself – jitter Jun 24 '09 at 15:25
I couldn't find the correct part in the third edition of the JLS. can anybody provide any further information? – Jon Jun 24 '09 at 16:16
Its the last point of the VM Specification chapter 4.10: http://java.sun.com/docs/books/jvms/second_edition/html/ClassFile.doc.html#88659 – user85421 Nov 27 '09 at 22:10
For Java 8: https://docs.oracle.com/javase/specs/jvms/se7/html/jvms-4.html#jvms-4.4.7 – Christopher Schultz Feb 07 '18 at 21:40

score 3 · Answer 3 · answered Oct 29 '09 at 07:24

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With JDK 1.5, the practical limit for class names on Windows XP with 255 -- longer names gave errors in the file system. This was the full name (directory+package+class).

I have not tried JDK 1.6 on Vista or windows 7, hopefully Sun fixed it to be the NTFS limit of 8000 or so.

answered Oct 29 '09 at 07:24

Stanleymit

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anyone know the answer to JDK 1,6+ ? – ycomp Oct 25 '15 at 17:14

score 0 · Answer 4 · answered Jun 24 '09 at 15:20

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No. Java doesn't impose any limit on the class name. But if you interfacing with other systems (e.g. JNI) its better to be on the safe side.

answered Jun 24 '09 at 15:20

lud0h

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That's called **undefined behavior**, and bad part of any specs )) – gavenkoa Jul 11 '14 at 06:40

Does Java have a limit on the class name length?

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