&& : Java Glossary

false && false → false
false && true → false
true && false → false
true && true → true

The evaluation is guaranteed to proceed in strict left to right order, and if any boolean is false, 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 try to test the length of s
if ( s != null && s.length() > 0 )
    {
    out.println( "non empty string" );
    }

Learning More