java _io_面向对象风格递归获得文件夹大小

public class test { private int sum; //文件夹大小 private String path; //路径 private File f; public static void main(String[]args) throws IOException { test t=new test("D:/d"); System.out.println(t.getSum()); } public test(String path) { this.path=path; this.f=new File(path); N(this.f); } public int getSum() { return this.sum; } //递归打印获得文件夹大小 private int N(File f) { if(null!=f&&f.exists()) { if(f.isFile()) //是文件才能获得大小 { sum+=f.length(); } else if(f.isDirectory()) { File[] ss=f.listFiles(); for(File r:ss) { N(r); } } } return sum; } }