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I know that a method cannot be larger than 64 KB with Java. The limitation causes us problems with generated code from a JavaCC grammar. We had problems with Java 6 and were able to fix this by changing the grammar. Has the limit been changed for Java 7 or is it planned for Java 8?
Just to make it clear. I don't need a method larger than 64 KB by myself. But I wrote a grammar which compiles to a very large method.
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The number of method parameters is limited to 255 by the definition of a method descriptor (§4.3. 3), where the limit includes one unit for this in the case of instance or interface method invocations. Section §4.3.
The number of methods that may be declared by a class or interface is limited to 65535 by the size of the methods_count item of the ClassFile structure (§4.1).
But a class can have 65535 attributes, plus 65535 fields, each of them having 65535 attributes of its own and plus 65535 methods, each of them having up to 65535 attribute as well.
Therefore, the maximum length of String in Java is 0 to 2147483647. So, we can have a String with the length of 2,147,483,647 characters, theoretically.
According to JVMS7 :
The fact that end_pc is exclusive is a historical mistake in the design of the Java virtual machine: if the Java virtual machine code for a method is exactly 65535 bytes long and ends with an instruction that is 1 byte long, then that instruction cannot be protected by an exception handler. A compiler writer can work around this bug by limiting the maximum size of the generated Java virtual machine code for any method, instance initialization method, or static initializer (the size of any code array) to 65534 bytes.
But this is about Java 7. There is no final specs for Java 8, so nobody (except its developers) could answer this question.
UPD (2015-04-06) According to JVM8 it is also true for Java 8.
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Good question. As always we should go to the source to find the answer ("The Java® Virtual Machine Specification"). The section does not explicitly mention a limit (as did the Java6 VM spec) though, but somewhat circumspectly:
The greatest number of local variables in the local variables array of a frame created upon invocation of a method (§2.6) is limited to 65535 by the size of the max_locals item of the Code attribute (§4.7.3) giving the code of the method, and by the 16-bit local variable indexing of the Java Virtual Machine instruction set.
Cheers,
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