public void addNode(final Instruction instruction){
  instructions.add(instruction);
  if (prevInstruction != null) {
    addEdge(prevInstruction,instruction);
  }
  prevInstruction=instruction;
}

public void addNode ( final Instruction instruction ) { instructions . add ( instruction ) ; if ( prevInstruction != null ) { addEdge ( prevInstruction , instruction ) ; } prevInstruction = instruction ; }
add new node and set prev instruction pointing to this instruction
