Selecting #of bits for data types in Java

Question

hi,
i would like to know if we can constrain compiler on allocating memory to basic data types, such as int, float, short etc. i would like to read an exactly four byte integer into an int, 2 byte short into a short etc. i need to read these parameters exactly of their specified number of bytes - not more or less - as if i read anything more/less, i will be reading a part of other parameter.
i know that C allows us to do this by letting us to specify number of bits we like to allocate for each data type (for eg. unsigned int:16; means i need an unsigned int of exactly 16bits (2 bytes long) -no more and no less).
Is there anything similar i can do in Java?
any suggestion is greately appreciated.
Thanks,

Answer 1

All primitive types in Java are well-defined. In contrast to C/C++, an int in Java is allways 32 bits, using one's complement, a char is allways 16 bits etc.
Java does not give you direct acces to physical memory - that would compromise the basic design of Java.
You can read individual bytes from files, and you can do all the integer arithmetic in Java as you can in C/C++. To convert eg. fout bytes to one int, you could do the following:
byte b1= (some byte value),
     b2,
     b3,
     b4;
int i= (((b1 << 8) | b2 << 8) | b3 << 8) | b4;
b1 being the most significant byte, b4 being the least significant.
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