java方法 调用 问题

public   class Writer { int n=0; String bookName; public   void addComputerB(String name) { ++n; bookName = name; try { FileWriter filew= new FileWriter(new File(“计算机类.txt”)); BufferedWriter br = new BufferedWriter(filew); br.write(bookName); br.newLine(); br.flush(); br.close(); filew.close(); } catch (IOException e) { // TODO Auto-generated catch block e.printStackTrace(); } } public String getName(String Bname) { return Bname; } public static void main(String[] args) { // TODO Auto-generated method stub addComputerB(getName(“《核心技术》”)); //为什么在此处提示有问题，说必须将方法改成静态的  啥原因呢？ System.out.println(n); }
}