int a, c, d;
boolean b;
...
int a = b ? c : d;
// or, with explicit parentheses:
int a = ( b ? c : d );
// is shorthand for:
if ( b )
   {
   a = c;
   }
else
   {
   a = d;
   }

// similarly:
int a, b, c, d, e;
...
e = a == b ? c : d;
// or, with explicit parentheses:
e = ( ( a == b ) ? c : d );
// is shorthand for:
if ( a == b )
   {
   e = c;
   }
else
   {
   e = d;
   }

// The way you most often get in trouble with ? : is this:
out.println (  ( big ? "elephant" : "mouse" ) + " is an animal.");

// The ( ) are mandatory. Without the ( ) it means:
out.println (  big ? "elephant" : ( "mouse"  + " is an animal.") );