question: public void addForce ( Force f ) { if ( f . isItemForce ( ) ) { if ( iforces . length == iflen ) { Force [ ] newf = new Force [ iflen + 10 ] ; System . arraycopy ( iforces , 0 , newf , 0 , iforces . length ) ; iforces = newf ; } iforces [ iflen ++ ] = f ; } if ( f . isSpringForce ( ) ) { if ( sforces . length == sflen ) { Force [ ] newf = new Force [ sflen + 10 ] ; System . arraycopy ( sforces , 0 , newf , 0 , sforces . length ) ; sforces = newf ; } sforces [ sflen ++ ] = f ; } }
target:  Add a new Force function to the simulator.