JAVA之IO--字节流(三)

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使用字节流进行文件操作

1、读取文件

一般步骤：1）建立连接 File—>2）选择流 InputStream —>3)操作 byte[]+read—>4)关闭

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@Test
	public void readFile() {
		// 1.建立连接 File
		File pom = new File("pom.xml");
		// 2.选择流
		InputStream in = null;
		try {
			in = new FileInputStream(pom);
			// 3.操作
			byte[] bytes = new byte[1024]; // 每次读取1024个字节
			int len = 0;// 接收读取的大小
			while ((len = in.read(bytes, 0, 1024)) != -1) {
				System.out.println(new String(bytes, 0, len));
			}
		} catch (FileNotFoundException e) {
			e.printStackTrace();
			System.out.println("文件不存在！");
		} catch (IOException e) {
			e.printStackTrace();
			System.out.println("读取文件失败!");
		} finally {
			//4.释放资源
			try {
				if (null != in) {
					in.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

2、写出文件

一般步骤：1）建立连接 File—>2）选择流 OutputStream —>3)write+flush—>4)关闭

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@Test
	public void writeFile() {
		// 1.建立联系 File
		File file = new File("test.txt");
		// 2.选择流
		OutputStream out = null;
		try {
			out = new FileOutputStream(file, true);// 表示写文件是追加还是覆盖
			// 3.操作
			String msg = "hello world!\n";
			byte[] data = msg.getBytes();
			out.write(data, 0, data.length);
			out.flush();// 强制刷新出去
		} catch (FileNotFoundException e) {
			e.printStackTrace();
			System.out.println("文件找不到!");
		} catch (IOException e) {
			e.printStackTrace();
			System.out.println("文件写出失败！");
		}finally {
			try {
				if (out != null) {
					out.close();
				} 
			} catch (IOException e) {
				e.printStackTrace();
				System.out.println("关闭失败!");
			}
		}
	}

3、文件的拷贝

就是将文件的读取和文件的写出就是文件的拷贝。

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@Test
	public void copyFile() {
		// 1.建立联系
		File inFile = new File("pom.xml");
		File outFile = new File("test.txt");
      
      	//只能拷贝文件
      	if(inFile.isFile){
          return;
      	}
		// 2.选择流
		InputStream in = null;
		OutputStream out = null;
		try {
			in = new FileInputStream(inFile);
			out = new FileOutputStream(outFile);
			// 3.操作
			byte[] bytes = new byte[1024];
			int len = 0;
			while ((len = in.read(bytes, 0, 1024)) != -1) {
				out.write(bytes, 0, len);
			}
			out.flush();// 强制刷新
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			try {
				if (out != null) {
					out.close();
				}
				if (in != null) {
					in.close();
				}
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
	}

4、文件夹的拷贝

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@Test
	public void copyFile2() {
		File inFile = new File("src");
		File outFile= new File("outSrc");
		try {
			copy(inFile,outFile);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	private void copy(File inFile, File outFile) throws IOException {
		File nowOut = new File(outFile,inFile.getName()); //需要拷贝的文件名称
		if(inFile.isDirectory()) {
			nowOut.mkdirs(); //如果是目录就创建目录
			for (File subFile : inFile.listFiles()) {
				copy(subFile,nowOut); //递归调用
			}
		}else {
			//如果是文件就进行拷贝
			InputStream in = new FileInputStream(inFile);
			OutputStream out = new FileOutputStream(nowOut);
			byte[] bytes = new byte[1024];
			int len = 0;
			while((len=in.read(bytes, 0, 1024))!=-1) {
				out.write(bytes, 0, len);
			}
			out.flush();
			out.close();
			in.close();
		}
	}