Input and Output - Java - page 381

double double tmp ;

while while ( scan . hasNext ()) {

iif ( scan . hasNextDouble ()) {
push ( scan . nextDouble ());
} else else {

String token = scan . next ();
iif ( token . equals ( "+" )) {
// Found + operator, perform it immediately.
push ( pop () + pop ());
} else else iif ( token . equals ( "-" )) {

// Found - operator, perform it (order matters).
tmp = pop ();
push ( pop () - tmp );
} else

else iif ( token . equals ( "*" )) {
// Multiply is commutative
push ( pop () * pop ());
} else

else iif ( token . equals ( "/" )) {
// Handle division carefully: order matters!
tmp = pop ();
push ( pop () / tmp );
} else

else iif ( token . equals ( "=" )) {
out . println ( peek ());
} else else {

out . println ( "What's this? " + token );

}

}

}

}

void void push ( double double val ) {

s . push ( new

new Double ( val ));

}

double double pop () {

return return (( Double ) s . pop ()). doubleValue ();

}

double double peek () {

return return (( Double ) s . peek ()). doubleValue ();

}

void void clearStack () {

s . removeAllElements ();

}

}