this.label = id;
	public BasicBlock(int id) {		this.id = id;		this.firstInstruction = null;		this.lastInstruction = null;		this.exceptionThrower = null;		this.exceptionGen = null;		// Each block maintains a list of incoming and outgoing edges.		// These are used by the CFG class.		this.firstIncomingEdge = null;		this.lastIncomingEdge = null;		this.firstOutgoingEdge = null;		this.lastOutgoingEdge = null;	}