How does Java deal with multiple conditions inside a single IF statement

Question

Lets say I have this:

if(bool1 && bool2 && bool3) {
...
}

Now. Is Java smart enough to skip checking bool2 and bool2 if boo

Answer 1

Please look up the difference between & and && in Java (the same applies to | and ||).

& and | are just logical operators, while && and || are conditional logical operators, which in your example means that

if(bool1 && bool2 && bool3) {

will skip bool2 and bool3 if bool1 is false, and

if(bool1 & bool2 & bool3) {

will evaluate all conditions regardless of their values.

For example, given:

boolean foo() {
    System.out.println("foo");
    return true;
}

if(foo() | foo()) will print foo twice, and if(foo() || foo()) - just once.

Answer 2

Yes, Java (similar to other mainstream languages) uses lazy evaluation short-circuiting which means it evaluates as little as possible.

This means that the following code is completely safe:

if(p != null && p.getAge() > 10)

Also, a || b never evaluates b if a evaluates to true.

Answer 3

Is Java smart enough to skip checking bool2 and bool2 if bool1 was evaluated to false?

Its not a matter of being smart, its a requirement specified in the language. Otherwise you couldn't write expressions like.

if(s != null && s.length() > 0)

or

if(s == null || s.length() == 0)

BTW if you use & and | it will always evaluate both sides of the expression.

Answer 4

Yes,that is called short-circuiting.

Please take a look at this wikipedia page on short-circuiting