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And here are the corresponding declarations and literals:

1. The attributes of the primitive data types were chosen to enhance portability and distributability:
   • Each primitive type has a fixed size, regardless of platform
   • Unlike C and C++, where, depending on the platform:
     • an int may be 16, 32, or 64 bits, or larger
     • a char may be signed or unsigned
   • Each primitive type has fixed semantics, regardless of platform
     • Unlike C and C++, where, depending on the platform:
       • integer datatypes may be 2's-complement, 1's-complement, or whatever
       • floating point datatypes may be IEEE, or other floating point formats.
       • platforms may use big-endian or little-endian semantics
2. They were also chosen to enhance safety:
   • Initial/default values of primitive types are well-defined
     • Unlike C and C++, where they are undefined for auto variables.
       • Probably the most common cause of bugs in C and C++
   • Java has no unsigned integers and no unsigned keyword
     • Unlike C and C++, where you can mix signed and unsigned arithmetic
       • The source of many subtle bugs in C and C++
   • Java distinguishes between char and byte (and short)
     • Unlike C and C++, where char may be:
       • either a character, or a 'tiny integer'
       • signed or unsigned (the source of subtle bugs, and portability problems)
   • Java strings (including string literals) are true objects (see later)
     • Unlike C and C++, where they are simply arrays of char
   • Java has a boolean type which is not an integer
     • Unlike C, which uses integers instead
       • C programs typically intermix integers and booleans in cavalier fashion
     • C++ now has a bool data type, but it was not in the original C++ proposals.
       • C++ programs typically intermix integers and bools in the same cavalier fashion, due to the lack of a true boolean type in many C++ compilers (also because of programmer laziness!)
3. They were also chosen to enhance internationalizability:
   • Java uses Unicode
     • for Java characters
     • for Java strings
     • for Java identifiers
   • Unicode:
     • is a 16-bit character encoding
     • encompasses the characters from many different languages
     • the first 128 characters are the same as the ASCII character set
     • the first 256 characters are the same as the ISO8859-1 (Latin-1) character set
     • Java uses all the standard C escapes, like \n, \t, \r, \xxx (where xxx is three octal digits) etc.
     • Java uses \uxxxx (where xxxx is four hex digits)
     • Java does not support line continuation using \

Examples of the Use of Primitive Data Types

boolean isOld;
int age = 52;
...
isOld = (age > 50);
if (isOld)
    PayPension();

char c = 'A';
char newline = '\n';
char apostrophe = '\'';
char delete = '\377';
char aleph = '\u0500';

byte by = 45;
short sh = -323;
int i = 04567;
long lng = 0x08DADL;		

float  across = 45.67f;
double cross  = -123e-23;

This page was last modified on 02 October, 2007