fix(java): Set the default maximum value for XdrString.

[overcat]

XDR RFC document states

Counted
byte strings are declared as follows:

     string object<m>;
  or
     string object<>;

The constant m denotes an upper bound of the number of bytes that a
string may contain. If m is not specified, as in the second
declaration, it is assumed to be (2**32) - 1, the maximum length.

As an example of testing code, here are the .x file and the generated code. Such code cannot pass compilation.

xdrgen/spec/fixtures/generator/test.x

Line 10 in 48fffac

typedef string str2<>;

decodedStr2.str2 = XdrString.decode(stream, );

So we need to set a default maximum value for it. According to the protocol, it should be (2**32) - 1, but due to Java's limitations*, we used int to store the maximum value, so we have set it as (2**31) - 1. I believe this should meet our requirements as in practical business scenarios, the length of strings we use will not exceed this value.

Java's limitations:

• xdrgen/lib/xdrgen/generators/java/XdrString.erb

  Line 30 in 48fffac

  byte[] bytes = new byte[size];

• https://stackoverflow.com/questions/1071858/java-creating-byte-array-whose-size-is-represented-by-a-long

[overcat]

Hi @tamirms, can you review and merge this PR?

[tamirms]

@overcat could you explain why this PR is necessary?

[overcat]

@overcat could you explain why this PR is necessary?

I have added the reasons above, please check it.

[overcat]

The previous code fails to compile.