Numbers - Java - page 179

System . out . println ( da + " != " + db );

}

System . out . println ( "NaN prints as " + Double . NaN );

// Show that comparing two NaNs is not a good idea:
double

double nan1 = Double . NaN ;
double double nan2 = Double . NaN ;

iif ( nan1 == nan2 )
System . out . println ( "Comparing two NaNs incorrectly returns true." );

else else

System . out . println ( "Comparing two NaNs correctly reports false." );

iif ( new new Double ( nan2 )))

System . out . println ( "Double(NaN).equals(NaN) correctly returns true." );

new Double ( nan1 ). equals ( new

else else

System . out . println ( "Double(NaN).equals(NaN) incorrectly returns false." );

}

/** Compare two doubles within a given epsilon */
public

public static static boolean boolean equals ( double double a , double double b , double double eps ) {

iif ( a == b ) return true ;

// If the difference is less than epsilon, treat as equal.
return

return true

return Math . abs ( a - b ) < eps ;

}

/** Compare two doubles, using default epsilon */
public

public static static boolean boolean equals ( double double a , double double b ) {

return return equals ( a , b , EPSILON );

}

}

Note that neither of the System.err messages about “incorrect returns” prints. The point of
this example with NaN s is that you should always make sure values are not NaN before en-
trusting them to Double.equals() .

Rounding Floating-Point Numbers

Problem

You need to round floating-point numbers to integers or to a particular precision.