and

[Nick George]

So, by playing the Rules Roundup, it has come to my attention that I can just as correctly write

if( x<5 & y>3)

as

if( x<5 && y>3)

so why have I, up until this point, always written &&, and always seen it written as &&?

[Edwin Keeton]

 && 

is a "short-circuit" boolean operation. So if the first (left-to-right) expression evaluates false, the second expression is not evaluated since false and true evaluates false.

 & 

evaluates both expressions regardless. This is significant if your code depends on the second expression being evaluated or not.

[Tim Holloway]

if ( (1 > 2) && deleteAllMyFiles() ) {
System.out.println("This can never happen");
}

[Layne Lund]

Originally posted by Tim Holloway:
if ( (1 > 2) && deleteAllMyFiles() ) {
System.out.println("This can never happen");
}

As Edwin explains above, this snippet will not only skip the println() call, but it will also skip deleteAllMyFiles().

Layne

[Nick George]

Roger

[Stan James]

I recently found this in code:

if( a != null & a.equals("b") ) ...

which still gets a null pointer exception when a is null. They intended a shortcut && in there to make that work. Being a PITA I changed it to:

if ( "b".equals(a) ) ...