Decisions - Java Concepts - page 259

Java has six relational operators:

Java Math Notation Description

> >

Greater than

>= >

Greater than or equal

< <

Less than

<= <

Less than or equal

== =

Equal

!= ¬

Not equal

As you can see, only two relational operators ( > and < ) look as you would expect
from the mathematical notation. Computer keyboards do not have keys for ² ± , or
¬ , but the >= , <= , and != operators are easy to remember because they look
similar.

The == operator is initially confusing to most newcomers to Java. In Java, the =
symbol already has a meaning, namely assignment. The == operator denotes
equality testing:

a = 5; // Assign 5 to a
if (a == 5) . . . // Test whether a equals 5

You will have to remember to use == for equality testing, and to use = for
assignment.

5.2.2 Comparing Floating-Point Numbers

You have to be careful when comparing floating-point numbers, in order to cope
with roundoff errors. For example, the following code multiplies the square root of
2 by itself and then subtracts 2.

double r = Math.sqrt(2);
double d = r * r - 2;
if (d == 0)
System.out.println("sqrt(2) squared minus 2 is
0");
else
System.out.println(
"sqrt(2) squared minus 2 is not 0 but
" + d);

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