java file对象获取文件大小

import java.io.File;
import java.text.DecimalFormat;
import java.io.FileInputStream;

public class GetFileSize
{
    public longgetFileSizes(File f) throws Exception{//取得文件大小
       long s=0;
       if (f.exists()) {
           FileInputStream fis = null;
           fis = new FileInputStream(f);
          s= fis.available();
       } else {
           f.createNewFile();
           System.out.println("文件不存在");
       }
       return s;
    }
    // 递归
    public longgetFileSize(File f)throws Exception//取得文件夹大小
    {
       long size = 0;
       File flist[] = f.listFiles();
       for (int i = 0; i < flist.length; i++)
       {
           if (flist[i].isDirectory())
           {
               size = size + getFileSize(flist[i]);
           } else
           {
               size = size + flist[i].length();
           }
       }
       return size;
    }

    publicString FormetFileSize(long fileS) {//转换文件大小
       DecimalFormat df = new DecimalFormat("#.00");
       String fileSizeString = "";
       if (fileS < 1024) {
           fileSizeString = df.format((double) fileS) + "B";
       } else if (fileS < 1048576) {
           fileSizeString = df.format((double) fileS / 1024) + "K";
       } else if (fileS < 1073741824) {
           fileSizeString = df.format((double) fileS / 1048576) + "M";
       } else {
           fileSizeString = df.format((double) fileS / 1073741824) +"G";
       }
       return fileSizeString;
    }
   
    public longgetlist(File f){//递归求取目录文件个数
       long size = 0;
       File flist[] = f.listFiles();
       size=flist.length;
       for (int i = 0; i < flist.length; i++) {
           if (flist[i].isDirectory()) {
               size = size + getlist(flist[i]);
               size--;
           }
       }
       return size;

 

   }
   
    publicstatic void main(String args[])
    {
       GetFileSize g = new GetFileSize();
       long startTime = System.currentTimeMillis();
       try
       {
           long l = 0;
           String path = "C:\\WINDOWS";
           File ff = new File(path);
           if (ff.isDirectory()) { //如果路径是文件夹的时候
               System.out.println("文件个数          " + g.getlist(ff));
               System.out.println("目录");
               l = g.getFileSize(ff);
               System.out.println(path + "目录的大小为：" + g.FormetFileSize(l));
           } else {
               System.out.println("    文件个数          1");
               System.out.println("文件");
               l = g.getFileSizes(ff);
               System.out.println(path + "文件的大小为：" + g.FormetFileSize(l));
           }