Java For Dummies Quick Reference

Casting

Casting is used to convert data of one type to another. For example, you can use casting to convert a double to an int.

For more information on the int or double data types, see Integer Data Types and Floating-point Data Types.

When you use casting, you run the risk of losing information. A double can hold larger numbers than an int, for example. In addition, an int can’t hold the fractional part of a double. As a result, if you cast a double to an int, you run the risk of losing data or accuracy — so 3.1415 becomes 3, for example.

Casting does not round numbers up. For example:

double price = 9.99;

int iPrice = (int) price;

Here, iPrice is assigned the value 9. If you want to round the double value when you convert it, use the round method of the Math class, as described within Math Class in Part 3.

To cast a value from one type to another, you use a cast operator, which is simply the name of a primitive type in parentheses placed before the value you want to cast. For example:

double pi = 3.1314;

int iPi;

iPi = (int) pi;

For more information about rounding, see Math Class ...