一、 创建
1. 创建文档：createNewFile()
File f1 = new File("/Users/**/Documents/dev/fileTest/a.txt"); try { boolean b = f1.createNewFile(); //如果已经存在该文件，则返回false，不存在则返回true，成功创建 System.out.println(b); } catch (IOException e) { e.printStackTrace(); } 2. 创建文件夹：mkdir()和mkdirs()
File file = new File("/Users/**/Documents/dev/fileTest/a");boolean b = file.mkdir();//如果已经存在该文件夹，则返回false，不存在则返回true，成功创建.//boolean b = file.mkdirs();//创建多级目录System.out.println(b); 二、删除文件：delete()和deleteOnExit()
File file = new File("/Users/**/Documents/dev/fileTest/a.txt");// file.delete(); //手动删除文件 file.deleteOnExit(); //程序退出时自动删除文件 三、查询文件
1、是否存在：exists()
File file = new File("/Users/**/Documents/dev/fileTest/a.txt");boolean b = file.exists();//如果已经存在，则返回true，不存在则返回falseSystem.out.println(b); 2、isDirectory()：判断是否为文件夹；
3、isFile()：判断是否为文件；等等...
参考于：
四、读取文件
采用Reader是非常方便的，比如FileReader，InputStreamReader和BufferedReader。其中最重要的类是InputStreamReader， 它是字节转换为字符的桥梁。你可以在构造器重指定编码的方式，如果不指定的话将采用底层操作系统的默认编码方式，例如GBK等
1. FileInputStream
一次单个字节读取
File file = new File("/Users/**/Documents/dev/fileTest/a.txt"); InputStream in = null; try { in = new FileInputStream(file);//以字节为单位读取文件内容，一次读一个字节 换行也会自动换行 int tempbyte; while ((tempbyte = in.read()) != -1) { System.out.write(tempbyte); } in.close(); } catch (IOException e) { e.printStackTrace(); return; } 用 byte[] bt = new byte[100] 一次多个字节（自定义）读取
File file = new File("/Users/**/Documents/dev/fileTest/a.txt"); byte[] bt = new byte[100]; InputStream in = null; try { in = new FileInputStream(file);//以字节为单位读取文件内容，一次读一个字节 int i; while ((i = in.read(bt)) != -1) { System.out.write(bt,0,i); } in.close(); } catch (IOException e) { e.printStackTrace(); return; } 2. InputStreamReader
一次一个char字符读取
File file = new File("/Users/**/Documents/dev/fileTest/a.txt"); Reader in = null; try { in = new InputStreamReader(new FileInputStream(file),"utf8"); int i = 0; while ((i = in.read()) != -1) { System.out.write(i); } in.close(); } catch (IOException e) { e.printStackTrace(); return; } 一次多个char字符读取
File file = new File("/Users/**/Documents/dev/fileTest/a.txt"); char[] tempchars = new char[30]; Reader in = null; try { in = new InputStreamReader(new FileInputStream(file),"utf8"); int i = 0; while ((i = in.read(tempchars)) != -1) { System.out.print(tempchars); } in.close(); } catch (IOException e) { e.printStackTrace(); return; } 3. BufferedReader：按正行读取
File file = new File("/Users/**/Documents/dev/fileTest/a.txt"); BufferedReader reader = null; try { reader = new BufferedReader(new FileReader(file)); String str = ""; while ((str = reader.readLine()) != null) { System.out.print("\n"+str); } reader.close(); } catch (IOException e) { e.printStackTrace(); return; } 4. FileReader
File file = new File("/Users/**/Documents/dev/fileTest/a.txt"); FileReader reader = null; try { reader = new FileReader(file); int i = 0; while ((i = reader.read()) != -1) { System.out.write(i); } reader.close(); } catch (IOException e) { e.printStackTrace(); return; } 五、写入文档
1.InputStream转为OutputStream
File fileI = new File("/Users/bob/Documents/dev/fileTest/a.txt"); File fileO = new File("/Users/bob/Documents/dev/fileTest/b.txt"); try { InputStream it = new FileInputStream(fileI); OutputStream os = new FileOutputStream(fileO); byte flush[] = new byte[1024]; int len = 0; while(0<=(len=it.read(flush))){ os.write(flush, 0, len); } //关闭流注意: 先打开的后关 os.close(); it.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } 2.写入一串字符
File fileO = new File("/Users/**/Documents/dev/fileTest/b.txt"); try { PrintWriter w = new PrintWriter(new OutputStreamWriter( new FileOutputStream(fileO), "utf8")); w.write("hello world 你好世界"); w.close(); } catch (FileNotFoundException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); }