|| : Java Glossary

||

Performs a short-circuit logical or, on two booleans. || is sometimes called the short circuit “or” operator or the McCarthy “or” operator. John McCarthy was one of the LISP pioneers. The | character is created by hitting shift-\. Sometimes it is displayed with a small gap in the bar, sometimes not. It can be hard to tell apart from Il1! in some fonts.

false || false → false
false || true → true
true || false → true
true || true → true

The evaluation is guaranteed to proceed in strict left to right order, and if any boolean is true, it does not evaluate any expressions to the right of that. This lets you write code like this:

// if s is null, Java won't bother to test the length of s
if ( s == null || s.length() == 0 )
   {
   out.println( "empty string" );
   }

Learning More

Sun’s JLS: Java Language Specification: expression evaluation order

&
&&
binary
bit
boolean
|

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