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JavaIO

程序员文章站 2022-06-13 21:20:35
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一、IO 流的结构

JavaIO

二、IO流的划分

   1 按照流的流向的不同：输入流   输出流  (站位于程序的角度)
   2 按照流中的数据单位的不同：字节流   字符流  （纯文本文件使用字符流 ，除此之外使用字节流）
   3 按照流的角色的不同：节点流   处理流   （流直接作用于文件上是节点流（4个），除此之外都是处理流）

三、实现

1、字节流文件复制

/**
	 * 实现字节文件的复制
	 * 
	 * @param src源文件路径
	 * @param dest目标文件路径
	 */
	public void copyFile(String src, String dest) {
		File file1 = new File(src);// 源文件
		File file2 = new File(dest);// 目标文件

		BufferedInputStream bis = null;
		BufferedOutputStream bos = null;
		try {
			FileInputStream fis = new FileInputStream(file1);
			FileOutputStream fos = new FileOutputStream(file2);

			bis = new BufferedInputStream(fis);
			bos = new BufferedOutputStream(fos);

			byte[] b = new byte[1024];
			int len;
			while ((len = bis.read(b)) != -1) {
				bos.write(b, 0, len);
			}
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			if (bos != null) {
				try {
					bos.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			if (bis != null) {
				try {
					bis.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}

2、字符文件复制

	public void copyFile2(String src, String dest) {
		File file1 = new File(src);
		File file2 = new File(dest);

		BufferedReader br = null;
		BufferedWriter bw = null;

		try {

			FileReader fr = new FileReader(file1);
			FileWriter fw = new FileWriter(file2);
			br = new BufferedReader(fr);
			bw = new BufferedWriter(fw);

			// 按字符读
//			char[] c = new char[1024];
//			int len;
//			while((len=br.read(c)) != -1) {
//				bw.write(c, 0, len);				
//			}

			// 按行读
			String str = null;
			while ((str = br.readLine()) != null) {
				bw.write(str);
				bw.newLine();
			}

		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			if (br != null) {
				try {
					br.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
			if (bw != null) {
				try {
					bw.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}

	}

3、转换流文件复制

/**
	 * 转换流输入输出 
	 * 编码 字符串---->字节数组 
	 * 解码 字节数组---->字符串
	 * 
	 * @param src
	 * @param dest
	 */
	public void copyFile(String src, String dest) {
		File file1 = new File(src);
		File file2 = new File(dest);

		BufferedReader br = null;
		BufferedWriter bw = null;
		try {
			FileInputStream fis = new FileInputStream(file1);
			InputStreamReader isr = new InputStreamReader(fis);
			br = new BufferedReader(isr);

			FileOutputStream fos = new FileOutputStream(file2);
			OutputStreamWriter osw = new OutputStreamWriter(fos);
			bw = new BufferedWriter(osw);

			String str;
			while ((str = br.readLine()) != null) {
				bw.write(str);
				bw.newLine();
			}
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		} finally {
			if (bw != null) {
				try {
					bw.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
			if (br != null) {
				try {
					br.close();
				} catch (IOException e) {
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}

	}

4、基于转换流的控制台输入小案例

public class MyInput {

	public String nextString() {
		String str = null;
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		try {
			str = br.readLine();

		} catch (IOException e) {
			e.printStackTrace();
		}
		return str;
	}

	public int nextInt() {
		return Integer.parseInt(nextString());
	}

	public boolean nextBoolean() {
		return Boolean.parseBoolean(nextString());
	}

	public static void main(String[] args) {
		MyInput in = new MyInput();
		String nextString = in.nextString();
		System.out.println(nextString);
		int nextInt = in.nextInt();
		System.out.println(nextInt);
		boolean nextBoolean = in.nextBoolean();
		System.out.println(nextBoolean);

	}

}

5、打印输出流

    @Test
	public void testPrintStreamWriter() {
		FileOutputStream fos = null;
		try {
			fos = new FileOutputStream(new File("text.txt"));
		} catch (FileNotFoundException e) {
			e.printStackTrace();
		} // 创建打印输出流,设置为自动刷新模式(写入换行符或字节 '\n' 时都会刷新输出缓冲区)
		PrintStream ps = new PrintStream(fos, true);
		if (ps != null) { // 把标准输出流(控制台输出)改成文件
			System.setOut(ps);
		}
		for (int i = 0; i <= 255; i++) { // 输出ASCII字符
			System.out.print((char) i);
			if (i % 50 == 0) { // 每50个数据一行
				System.out.println(); // 换行
			}
		}
		ps.close();

	}

6、DataWrite&DataRead

    @Test
	public void testDataWrite()	{
		DataOutputStream dos = null;
		try {
			FileOutputStream fos = new FileOutputStream(new File("data.txt"));
			dos = new DataOutputStream(fos);
			dos.writeInt(3);
			dos.writeUTF("你好");
			dos.writeBoolean(true);
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			if(dos != null) {
				try {
					dos.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}			
		}
		
	}
    @Test
	public void testDataRead(){
		DataInputStream dis = null;
		
		try {
			FileInputStream fis = new FileInputStream(new File("data.txt"));
			dis = new DataInputStream(fis);
			int readInt = dis.readInt();
			String readUTF = dis.readUTF();
			boolean readBoolean = dis.readBoolean();
			System.out.println(readInt);
			System.out.println(readUTF);
			System.out.println(readBoolean);
		}  catch (IOException e) {
			e.printStackTrace();
		}	finally {
			if(dis != null) {
				try {
					dis.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		
	}

7、ObjectInputStream&ObjectOutputStream（序列化）

public class TestObjectInputOutputStream {
	
	@Test
	public void testObejctInputStream() {
		ObjectInputStream ois =null;
		try {
			ois = new ObjectInputStream(new FileInputStream(new File("person.txt")));
			Person p1 = (Person) ois.readObject();
			System.out.println(p1);
			Person p2 = (Person) ois.readObject();
			System.out.println(p2);
		} catch (IOException e) {
			e.printStackTrace();
		} catch (ClassNotFoundException e) {
			e.printStackTrace();
		} finally {
			if(ois != null) {				
				try {
					ois.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
		
	}
	
	
	@Test
	public void testObjectOutputStream() {
		Person p1 = new Person("小红", 33);
		Person p2 = new Person("小明", 25);
		
		ObjectOutputStream oos = null;;
		try {
			oos = new ObjectOutputStream(new FileOutputStream(new File("person.txt")));
			oos.writeObject(p1);
			oos.writeObject(p2);;
		}  catch (IOException e) {
			e.printStackTrace();
		} finally {
			if(oos != null) {
				try {
					oos.close();
				} catch (IOException e) {
					e.printStackTrace();
				}		
			}
		}
		
				
	}
	
}

class Person implements Serializable{
	private static final long serialVersionUID = -2614025952162968968L;
	String name;
	Integer age;
	public Person(String name, Integer age) {
		super();
		this.name = name;
		this.age = age;
	}
	@Override
	public String toString() {
		return "Person [name=" + name + ", age=" + age + "]";
	}
}

8、RandomAccessFile

// 实现插入
	@Test
	public void test4() {
		RandomAccessFile raf = null;
		try {
			raf = new RandomAccessFile(new File("hello5.txt"), "rw");

			raf.seek(4);//插入位置4

			byte[] b = new byte[10];
			int len;
			StringBuffer sb = new StringBuffer();
			while ((len = raf.read(b)) != -1) {
				sb.append(new String(b, 0, len));
			}

			raf.seek(4);
			raf.write("xyz".getBytes());

			raf.write(sb.toString().getBytes());
		} catch (IOException e) {
			e.printStackTrace();
		} finally {
			if (raf != null) {
				try {
					raf.close();
				} catch (IOException e) {
					e.printStackTrace();
				}
			}
		}
	}

 

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