Decisions - Java Concepts - page 290

!(A || B) is the same as !A && !B

Pay particular attention to the fact that the and and or operators are reversed by
moving the not inwards. For example, the negation of Ȓthe input is S or the input
is Mȓ,

! (input.equals("S") || input.equals("M"))

is Ȓthe input is not S and the input is not Mȓ

!input.equals("S") && !input.equals("M")

Let us apply the law to the negation of ȓthe amount is between 0 and 1000ȓ:

! (0 < amount && amount < 1000)

is equivalent to

!(0 < amount) || !(amount < 1000)

which can be further simplified to

0 >= amount || amount >= 1000

Note that the opposite of < is >= , not >!

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5.4.4 Using Boolean Variables

You can use a Boolean variable if you know that there are only two possible values.
Have another look at the tax program in Section 5.3.2 . The marital status is either
single or married. Instead of using an integer, you can use a variable of type
boolean :

You can store the outcome of a condition in a Boolean variable.

private boolean married;

The advantage is that you can't accidentally store a third value in the variable.

Then you can use the Boolean variable in a test:

if (married)
. . .