many iterative calculations, or are manipulating large-valued numbers, double is the best
Here is a short program that uses double variables to compute the area of a circle:
// Compute the area of a circle.
class Area {
public static void main(String args[]) {
double pi, r, a;
r = 10.8; // radius of circle
pi = 3.1416; // pi, approximately
a = pi * r * r; // compute area
System.out.println("Area of circle is " + a);
In Java, the data type used to store characters is char. However, C/C++ programmers beware:
char in Java is not the same as char in C or C++. In C/C++, char is 8 bits wide. This is not the
case in Java. Instead, Java uses Unicode to represent characters. Unicode defines a fully
international character set that can represent all of the characters found in all human
languages. It is a unification of dozens of character sets, such as Latin, Greek, Arabic, Cyrillic,
Hebrew, Katakana, Hangul, and many more. For this purpose, it requires 16 bits. Thus, in
Java char is a 16-bit type. The range of a char is 0 to 65,536. There are no negative chars.
The standard set of characters known as ASCII still ranges from 0 to 127 as always, and the
extended 8-bit character set, ISO-Latin-1, ranges from 0 to 255. Since Java is designed to
allow programs to be written for worldwide use, it makes sense that it would use Unicode to
represent characters. Of course, the use of Unicode is somewhat inefficient for languages such
as English, German, Spanish, or French, whose characters can easily be contained within 8 bits.
But such is the price that must be paid for global portability.
NOTE  More information about Unicode can be found at
Here is a program that demonstrates char variables:
// Demonstrate char data type.
class CharDemo {
public static void main(String args[]) {
char ch1, ch2;
ch1 = 88;  // code for X
ch2 = 'Y';
System.out.print("ch1 and ch2: ");
System.out.println(ch1 + " " + ch2);
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