Learning Java, 4th Edition

Math Utilities

Java supports integer and floating-point arithmetic directly in the language. Higher-level math operations are supported through the java.lang.Math class. As you may have seen by now, wrapper classes for primitive data types allow you to treat them as objects. Wrapper classes also hold some methods for basic conversions.

First, a few words about built-in arithmetic in Java. Java handles errors in integer arithmetic by throwing an ArithmeticException:

    int zero = 0;

    try {
        int i = 72 / zero;
    } catch ( ArithmeticException e ) {
        // division by zero
    }

To generate the error in this example, we created the intermediate variable zero. The compiler is somewhat crafty and would have caught us if we had blatantly tried to perform division by a literal zero.

Floating-point arithmetic expressions, on the other hand, don’t throw exceptions. Instead, they take on the special out-of-range values shown in Table 11-1.

Table 11-1. Special floating-point values

Value	Mathematical representation
POSITIVE_INFINITY	1.0/0.0
NEGATIVE_INFINITY	-1.0/0.0
NaN	0.0/0.0

The following example generates an infinite result:

    double zero = 0.0;
    double d = 1.0/zero;

    if ( d == Double.POSITIVE_INFINITY )
        System.out.println( "Division by zero" );

The special value NaN (not a number) indicates the result of dividing zero by zero. This value has the special mathematical distinction of not being equal to itself (NaN != NaN evaluates to true). Use Float.isNaN() or Double.isNaN() to test for NaN.

The java.lang.Math ...