Why its wrong in java:

Question

Hello friends i have a question to define id in java. why this define is wrong:

if(0<=hours<24)

but

if(0<=hours&&hours<24)

is true.

Every language has its own syntax. – kosa Dec 05 '13 at 23:06 — kosa, Dec 05 '13 at 23:06
Because that's the way the language works. – Oliver Charlesworth Dec 05 '13 at 23:06 — Oliver Charlesworth, Dec 05 '13 at 23:06

score 5 · Answer 1 · answered Dec 05 '13 at 23:06

5

The first one parses as

if((0<=hours)<24)

or (for example, if hours was >= 0)

if(true<24)

which is invalid as a boolean cannot be less than an int.

In fact, no languages than I recall, except Python, allow this kind of syntax.

answered Dec 05 '13 at 23:06

tckmn

57,719
27
114
156

score 1 · Answer 2 · answered Dec 05 '13 at 23:06

1

Because the first inequality evaluates to a boolean. So this becomes,

if (true <= 24)

In Java, comparison between boolean and integers are not defined.

answered Dec 05 '13 at 23:06

Martijn Courteaux

67,591
47
198
287

score 1 · Answer 3 · answered Dec 05 '13 at 23:06

1

This is because the type of 0<=hours is a boolean and the < operator does not work on boolean and int.

answered Dec 05 '13 at 23:06

sigpwned

6,957
5
28
48

score 1 · Answer 4 · answered Dec 05 '13 at 23:07

The first one is syntactically incorrect. If you want to compare a variable against two other expressions you should have a valid operator like and (&&). That's why the second one is correct.

if (0 <= hours && hours < 24)

Here you are saying if hours is greater than or equal to 0 and at the same time stricktly less than 24.

Why its wrong in java:

4 Answers4