Java 输入/输出——处理流（DataInputStream/DataOutputStream、ByteArrayInputStream/ByteArrayOutputStream）

　　DataInputStream和DataOutputStream分别继承字节流InputStream和OutputStream，它属于处理流，需要分别“套接”在InputStream和OutputStream类型的节点流上。

　　DataInputStream和DataOutputStream提供了可以存取与机器无关的Java原始类型数据（如int，double等）的方法。

　　DataInputStream和DataOutputStream的构造方法：

DataInputStream(InputStream in)
DataOutputStream(OutputStream out)

　　ByteArrayInputStream和ByteArrayOutputStream的构造器和方法：

Constructor	Description
`ByteArrayInputStream(byte[] buf)`	Creates a `ByteArrayInputStream` so that it uses `buf` as its buffer array.
`ByteArrayInputStream(byte[] buf, int offset, int length)`	Creates `ByteArrayInputStream` that uses `buf` as its buffer array.

All MethodsInstance MethodsConcrete Methods
Modifier and Type	Method	Description
`int`	`available()`	Returns the number of remaining bytes that can be read (or skipped over) from this input stream.
`void`	`close()`	Closing a `ByteArrayInputStream` has no effect.
`void`	`mark(int readAheadLimit)`	Set the current marked position in the stream.
`boolean`	`markSupported()`	Tests if this `InputStream` supports mark/reset.
`int`	`read()`	Reads the next byte of data from this input stream.
`int`	`read(byte[] b, int off, int len)`	Reads up to `len` bytes of data into an array of bytes from this input stream.
`void`	`reset()`	Resets the buffer to the marked position.
`long`	`skip(long n)`	Skips `n` bytes of input from this input stream.

Constructor	Description
`ByteArrayOutputStream()`	Creates a new byte array output stream.
`ByteArrayOutputStream(int size)`	Creates a new byte array output stream, with a buffer capacity of the specified size, in bytes.

All MethodsInstance MethodsConcrete MethodsDeprecated Methods
Modifier and Type	Method	Description
`void`	`close()`	Closing a `ByteArrayOutputStream` has no effect.
`void`	`reset()`	Resets the `count` field of this byte array output stream to zero, so that all currently accumulated output in the output stream is discarded.
`int`	`size()`	Returns the current size of the buffer.
`byte[]`	`toByteArray()`	Creates a newly allocated byte array.
`String`	`toString()`	Converts the buffer's contents into a string decoding bytes using the platform's default character set.
`String`	`toString(int hibyte)`	Deprecated. This method does not properly convert bytes into characters. As of JDK 1.1, the preferred way to do this is via the `toString(String enc)` method, which takes an encoding-name argument, or the `toString()`method, which uses the platform's default character encoding.
`String`	`toString(String charsetName)`	Converts the buffer's contents into a string by decoding the bytes using the named `charset`.
`void`	`write(byte[] b, int off, int len)`	Writes `len` bytes from the specified byte array starting at offset `off` to this byte array output stream.
`void`	`write(int b)`	Writes the specified byte to this byte array output stream.
`void`	`writeTo(OutputStream out)`	Writes the complete contents of this byte array output stream to the specified output stream argument, as if by calling the output stream's write method using `out.write(buf, 0, count)`.

 1 package com.zyjhandsome.io;
 2 
 3 import java.io.*;
 4 
 5 public class TestDataStream {
 6 
 7     public static void main(String[] args) {
 8         // TODO Auto-generated method stub
 9         ByteArrayOutputStream baos = new ByteArrayOutputStream();
10         DataOutputStream dos = new DataOutputStream(baos);
11         
12         try {
13             dos.writeDouble(Math.random());
14             dos.writeBoolean(true);
15             ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
16             // bais.available()方法返回其占用的字节数目，double（8-byte）+boolean（1-byte）=9-byte
17             System.out.println(bais.available());
18             DataInputStream dis = new DataInputStream(bais);
19             // 先存进去的是Double类型数据+Boolean类型的数据
20             // 因此在读取时，也应该给先读取Double类型数据+Boolean类型的数据
21             System.out.println(dis.readDouble());
22             System.out.println(dis.readBoolean());
23             dos.close();
24             dis.close();            
25         } catch (IOException e) {
26             // TODO Auto-generated catch block
27             e.printStackTrace();
28         }        
29     }
30 }

　　输出结果：

1 9
2 0.03791491702144656
3 true