Java The Complete Reference, Seventh Edition

390 Part II: The Java Library

Understanding isInfinite( ) and isNaN( )

FloatandDoubleprovide the methodsisInfinite( )andisNaN( ), which help when

manipulating two specialdoubleandfloatvalues. These methods test for two unique

values defined by the IEEE floating-point specification: infinity and NaN (not a number).

isInfinite( )returnstrueif the value being tested is infinitely large or small in magnitude.

isNaN( )returnstrueif the value being tested is not a number.

The following example creates twoDoubleobjects; one is infinite, and the other is not

a number:

// Demonstrate isInfinite() and isNaN()

class InfNaN {

public static void main(String args[]) {

Double d1 = new Double(1/0.);

Double d2 = new Double(0/0.);

System.out.println(d1 + ": " + d1.isInfinite() + ", " + d1.isNaN());

System.out.println(d2 + ": " + d2.isInfinite() + ", " + d2.isNaN());

}

}

This program generates the following output:

Infinity: true, false

NaN: false, true

Byte, Short, Integer, and Long

TheByte,Short,Integer, andLongclasses are wrappers forbyte,short,int, andlonginteger

types, respectively. Their constructors are shown here:

Byte(bytenum)

Byte(Stringstr) throws NumberFormatException

Short(shortnum)

Short(Stringstr) throws NumberFormatException

Integer(intnum)

Integer(Stringstr) throws NumberFormatException

Long(longnum)

Long(Stringstr) throws NumberFormatException

As you can see, these objects can be constructed from numeric values or from strings that

contain valid whole number values.

The methods defined by these classes are shown in Tables 16-3 through 16-6. As you

can see, they define methods for parsing integers from strings and converting strings back

into integers. Variants of these methods allow you to specify theradix,or numeric base, for

conversion. Common radixes are 2 for binary, 8 for octal, 10 for decimal, and 16 for hexadecimal.