Modified.java

package p;

public enum Direction {NORTH, SOUTH, EAST, WEST; // note semicolon here
	public Direction opposite() {
		switch (this) {
		case NORTH:
			return SOUTH;
		case SOUTH:
			return NORTH;
		case EAST:
			return WEST;
		case WEST:
			return EAST;
		default: return null;
		}
	}
}