io流

概念

• 设备之间的数据传输

• 对于程序来说，把数据传输到其他节点，成为输出，反之输入

• 分类

  • 输出流
    • 字节，实际存储最小单位（8 bit)
    • 字符，utf编码，两个字节为单位(16 bit)
  • 输入流，输出流
    • 同上

• 读文件步骤 （把大象拿出冰箱需要几步）

  • 打开文件，创建流对象，建立通道
  • 读取文件，通过管道处理数据
  • 关闭输入流，关闭管道

• 写文件 （把大象关进冰箱）

  • 打开文件
  • 写入
  • 关闭流

基本流

基本流	字节流	字符流
输入流	InputStream(抽象基类)	Reader(抽象基类)
输出流	OutputStrenam(抽象基类)	Writer(抽象基类)

文件流

文件流	字节流	字符流
输入流	FileInputStream	FileReader
输出流	FileOutputStrenam	FileWriter

• FileReader
  • 父类：InputStreamReader
  • 方法（父类）
    • void close() 关闭流
      • Closes the stream and releases any system resources associated with it.
    • String getEncoding() ？？？
      • Returns the name of the character encoding being used by this stream.
    • int read() 读取一个字节，并返回int
      • Reads a single character.
    • int read(char[] cbuf, int offset, int length) 读取到指定的字符串中，指定开始下表和长度
      • Reads characters into a portion of an array.
    • boolean ready() 是否可读
      • Tells whether this stream is ready to be read.
• FilteWriter
  • 父类：OutputStreamWriter
  • 方法（父类）
    • void close() 关闭流
      • Closes the stream and releases any system resources associated with it.
    • String getEncoding() **
      • Returns the name of the character encoding being used by this stream.
    • int read() 读一个char转int返回
      • Reads a single character.
    • int read(char[] cbuf, int offset, int length)给指定的字符数组里面读一些字符串，从指定下标，读取指定长度，返回读取了多少个字符
      • Reads characters into a portion of an array.
    • boolean ready() 是否可读
      • Tells whether this stream is ready to be read.

public void copyjava() {
	FileWriter fileWriter = null;
	FileReader fileReader = null;
	
	try {
		fileReader = new FileReader("file");
		fileWriter = new FileWriter("file.bak");
		char [] buff = new char[100];
		int realCount = fileReader.read(buff);
		while (realCount != -1) {
			fileWriter.write(buff, 0, realCount);
			realCount = fileReader.read(buff);
		}
		
	} catch (Exception e) {
		System.out.println(e.getMessage());
	}finally {
		if(fileReader!= null) {
			try {
				fileReader.close();
			} catch (IOException e) {
				e.printStackTrace();
			}
		}
		if(fileWriter != null){
			try {
				fileWriter.close();
			} catch (Exception e2) {
			}
		}
		
	}
}

缓冲流

处理流	字节流	字符流
输入流	BufferedInputStream	BufferedReader
输出流	BufferedOutputStrenam	BufferedWriter

• 包装字符(字节流)流，包装类
• 包装方式，关联
• fileReader -> BufferedReader
• fileWriter -> BufferedWriter
• 可以多层嵌套

对象流

• ObjectInputStream
• ObjectutputStrenam

@Test
public void test5() {
	FileOutputStream fos = null;
	BufferedOutputStream bos = null;
	ObjectOutputStream oos = null; // 它是字节流中的辈份最高
	
	try {
		fos = new FileOutputStream("二进制文件");
		bos = new BufferedOutputStream(fos);
		oos = new ObjectOutputStream(bos);
		
		oos.writeInt(15);
		oos.writeBoolean(true);
		oos.writeBoolean(false);
		oos.writeLong(20);
		oos.writeDouble(3.14);
		
		oos.writeUTF("abc我和你xxx好吗"); // 把字符串以UTF8编码方式写入文件
		
	} catch (Exception e) {
		e.printStackTrace();
	} finally {
		if (oos != null) {
			try {
				oos.close();
			} catch (Exception e2) {
			}
		}
	}
}