File subDir=new File("c:\\mp3");if(subDir.isDirectory()){   // 是目录}File mp3=new File("c:\\mp3\\avemaria.mp3");                    if(mp3.isFile()){   // 是文件}

File dir = new File(fromDir);String[] children = dir.list();for (int i=0; i<children.length; i++) {    String filename = children[i];    ...}

public static void copyFile(File sourceFile, File targetFile) throws IOException {        BufferedInputStream inBuff = null;        BufferedOutputStream outBuff = null;        try {            // 新建文件输入流并对它进行缓冲            inBuff = new BufferedInputStream(new FileInputStream(sourceFile));            // 新建文件输出流并对它进行缓冲            outBuff = new BufferedOutputStream(new FileOutputStream(targetFile));            // 缓冲数组            byte[] b = new byte[1024 * 5];            int len;            while ((len = inBuff.read(b)) != -1) {                outBuff.write(b, 0, len);            }            // 刷新此缓冲的输出流            outBuff.flush();        } finally {            // 关闭流            if (inBuff != null)                inBuff.close();            if (outBuff != null)                outBuff.close();        }    }

String folder=System.getProperty("java.io.tmpdir");