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).

package com.zyjhandsome.io;

import java.io.*;

public class TestDataStream {

    public static void main(String[] args) {
        // TODO Auto-generated method stub
        ByteArrayOutputStream baos = new ByteArrayOutputStream();
        DataOutputStream dos = new DataOutputStream(baos);
        
        try {
            dos.writeDouble(Math.random());
            dos.writeBoolean(true);
            ByteArrayInputStream bais = new ByteArrayInputStream(baos.toByteArray());
            // bais.available()方法返回其占用的字节数目，double（8-byte）+boolean（1-byte）=9-byte
            System.out.println(bais.available());
            DataInputStream dis = new DataInputStream(bais);
            // 先存进去的是Double类型数据+Boolean类型的数据
            // 因此在读取时，也应该给先读取Double类型数据+Boolean类型的数据
            System.out.println(dis.readDouble());
            System.out.println(dis.readBoolean());
            dos.close();
            dis.close();            
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }        
    }
}

　　输出结果：

9
0.03791491702144656
true