java之File用法

1.//封装文件或者文件夹

File file = new File("D:\\Project");        if(file.exists())        {            if(file.isDirectory())            {                System.out.println(file+" isDirectory");            }else            {                System.out.println(file+" isFile");            }        }else        {            file.mkdirs();        }        File file2 = new File("D:\\Project\\1.txt");        if(file2.exists())        {            if(file2.isDirectory())            {                System.out.println(file2+" isDirectory");            }else            {                System.out.println(file2+" isFile");            }        }else        {            file2.createNewFile();        }        File[] files = file.listFiles();        for (File f : files) {            System.out.println(f);        }             //获取可用目录        File[] listRoots = File.listRoots();        for (File file : listRoots) {            System.out.println(file);        }

2.对文件和文件夹的操作

System.out.println(file2.getAbsolutePath());        System.out.println(file2.getParent());        System.out.println(file2.getPath());        System.out.println(file2.getName());        File file3 = new File("D:\\Project\\2.txt");        //renameTo前提file3文件不存在，可当做是move文件并重命名，返回true        System.out.println(file2.renameTo(file3));

3.File对象作为参数传递给流的构造函数

        FileOutputStream out = new FileOutputStream(file3);        byte[] bytes = "abcdefgh".getBytes();        for (byte b : bytes) {            out.write(b);        }        out.close();        File file4 = new File("D:\\Project\\3.txt");        if(!file4.exists())        {           file4.createNewFile();           }        FileInputStream in = new FileInputStream(file3);        FileOutputStream out2 = new FileOutputStream(file4);        int b;        while ((b = in.read()) != -1) {            out2.write(b);        }        in.close();        out2.close();