Java IO Stream 总结
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Java IO Stream 总结
引自如下:
http://read.newbooks.com.cn/info/195946.html
Stream 是在编程语言中对输入输出的总称 (一种比喻的称谓。Stream 为流水,输入输出实际上就是指数据的流动,数据由一个地方运动的另一个地方,就像流水一样,程序员将输入输出比作流水,再恰当不过了。)
流按照其所载内容分类,大致可分为字节流和字符流两大类
字节流 (Byte Stream)
在计算机中,byte是相当于机器语言中的单词,他在Java中统一由InputStream和OutputStream作处理。
字符流(Character Stream)
而在编码体系中,一般采用Char(2 bytes), 他在Java中统一由Reader和Writer作处理。
InputStream, OutputStream, Reader和Writer, 作为在java.io.*包的顶级父类,定义了IO Process中最抽象的处理和规范。对于实际的应用,他们并不适用。于是根据各种实际的需要,由他们派生出来形式各样各具特色的子类。
下表概述了Java IO 常用Classes 的关系:
常用Java IO Classes 关系图
Byte
InputStream/ OutputStream
Node
Byte Stream
FileInputstream/ FileOutputStream
PipeInputStream/
PipeOutputStream
…
Processing Byte Stream
FilterInputStream/
FilterOutputStream
BufferInputStream/
BufferOutputStream
DataInputStream/
DataOutputStream
PrintStream
…
Byte 与 Char 通过 InputstreamReader 和 OutputStreamWriter 来转换
Char
Reader/Writer
Node
Char Stream
FileReader/FileWriter
PipeReader/PipeWriter
…
Processing Char Stream
BufferReader/
BufferWriter
PrintWriter
…
(一)Stream的分类:
1 Node Stream :基本流,可以从名称中看出他是从哪个地方输入输出的。
1.1 用于文件输入输出流: FileInputStream, FileOutputStream
1.2 用于内存数组的输入输出流:ByteArrayInputStream, ByteArrayOutputStream
1.3 用于字符串的输入输出流:StringArrayInputStream, StringArrayOutputStream
1.4 用于管道的输入输出流:PipedInputStream, PipeOutStream (用于线程间的交互)
….
2 Processing Stream: 处理流,是对Node Stream的加强和补充,可以看作是高级流。 要构造一个高级流通常要以一个基础流为基础(如通过构造函数的参数传入)
2.1 用于提高输入输出效率的缓冲流:BufferedInputStream, BufferedOutputStream
2.2 用于数据转化的数据流: DataInputStream (用于读取Java的Primitive Data Type) , DataOutputStream
2.3 8位转化为16位的流: InputStreamReader, OutputWriter (用于沟通byte 和Char )
2.4 打印流: PintStream
….
(二)几个重要的IO Classes
InputStream
abstract int
(可对应Char)
read()
Reads the next byte of data from the input stream
Reads the next byte of data from the input stream
int
read(byte[] b)
Reads some number of bytes from the input stream and stores them into the buffer array b.
Reads some number of bytes from the input stream and stores them into the buffer array b.
void
close()
Closes this input stream and releases any system resources associated with the stream. (Stream 用完之后要注意关闭!)
Closes this input stream and releases any system resources associated with the stream. (Stream 用完之后要注意关闭!)
OutputStream
abstract void
write(int b)
Writes the specified byte to this output stream.
Writes the specified byte to this output stream.
void
write(byte[] b)
Writes b.length bytes from the specified byte array to this output stream.
Writes b.length bytes from the specified byte array to this output stream.
void
close()
Closes this output stream and releases any system resources associated with this stream.
Closes this output stream and releases any system resources associated with this stream.
void
flush()
Flushes this output stream and forces any buffered output bytes to be written out. (不必等buffer满了再写出,强行把所有的东西都写出来)
Flushes this output stream and forces any buffered output bytes to be written out. (不必等buffer满了再写出,强行把所有的东西都写出来)
DataInputStream
能够读出在输入流中读出Java的基本数据类型(primitive data type),常在对输入流格式十分清楚的情况下使用.
boolean
readBoolean()
byte
readByte()
char
readChar()
double
readDouble()
float
readFloat()
int
readInt()
DataOutputStream
能够直接写出Java的基本数据类型
void
writeBoolean(boolean v)
Writes a boolean to the underlying output stream as a 1-byte value.
Writes a boolean to the underlying output stream as a 1-byte value.
void
writeByte(int v)
Writes out a byte to the underlying output stream as a 1-byte value.
Writes out a byte to the underlying output stream as a 1-byte value.
void
writeDouble(double v)
Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the underlying output stream as an 8-byte quantity, high byte first.
Converts the double argument to a long using the doubleToLongBits method in class Double, and then writes that long value to the underlying output stream as an 8-byte quantity, high byte first.
void
writeFloat(float v)
Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the underlying output stream as a 4-byte quantity, high byte first.
Converts the float argument to an int using the floatToIntBits method in class Float, and then writes that int value to the underlying output stream as a 4-byte quantity, high byte first.
void
writeInt(int v)
Writes an int to the underlying output stream as four bytes, high byte first.
Writes an int to the underlying output stream as four bytes, high byte first.
FileReader
Constructor Summary
FileReader(File file)
Creates a new FileReader, given the File to read from.
Creates a new FileReader, given the File to read from.
FileReader(String fileName)
Creates a new FileReader, given the name of the file to read from.
Creates a new FileReader, given the name of the file to read from.
FileWriter
Constructor Summary
FileWriter(File file)
Constructs a FileWriter object given a File object.
Constructs a FileWriter object given a File object.
FileWriter(File file, boolean append)
Constructs a FileWriter object given a File object.
Constructs a FileWriter object given a File object.
FileWriter(String fileName)
Constructs a FileWriter object given a file name.
Constructs a FileWriter object given a file name.
FileWriter(String fileName, boolean append)
Constructs a FileWriter object given a file name with a boolean indicating whether or not to append the data written.
Constructs a FileWriter object given a file name with a boolean indicating whether or not to append the data written.
PrintWriter 最好的Writer (提供了我们熟悉的println()方法)
Constructor Summary
PrintWriter(File file)
Creates a new PrintWriter, without automatic line flushing, with the specified file.
Creates a new PrintWriter, without automatic line flushing, with the specified file.
PrintWriter(OutputStream out)
Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream.
Creates a new PrintWriter, without automatic line flushing, from an existing OutputStream.
PrintWriter(Writer out)
Creates a new PrintWriter, without automatic line flushing.
Creates a new PrintWriter, without automatic line flushing.
void
println(boolean x)
Prints a boolean value and then terminates the line.
Prints a boolean value and then terminates the line.
void
println(char x)
Prints a character and then terminates the line.
Prints a character and then terminates the line.
void
println(double x)
Prints a double-divcision floating-point number and then terminates the line.
Prints a double-divcision floating-point number and then terminates the line.
void
println(float x)
Prints a floating-point number and then terminates the line.
Prints a floating-point number and then terminates the line.
void
println(long x)
Prints a long integer and then terminates the line.
Prints a long integer and then terminates the line.
void
println(Object x)
Prints an Object and then terminates the line.
Prints an Object and then terminates the line.
void
println(String x)
Prints a String and then terminates the line.
Prints a String and then terminates the line.
BufferedReader
int
read()
Reads a single character.
Reads a single character.
String
readLine()
Reads a line of text.
Reads a line of text.
void
close()
Closes the stream and releases any system resources associated with it.
Closes the stream and releases any system resources associated with it.
BufferedWriter
void
write(char[] cbuf, int off, int len)
Writes a portion of an array of characters.
Writes a portion of an array of characters.
void
write(String s, int off, int len)
Writes a portion of a String.
Writes a portion of a String.
void
close()
Closes the stream, flushing it first.
Closes the stream, flushing it first.
void
flush()
Flushes the stream.
Flushes the stream.
InputStreamReader
Constructor Summary
InputStreamReader(InputStream in)
Creates an InputStreamReader that uses the default charset.
Creates an InputStreamReader that uses the default charset.
OutputStreamWriter
Constructor Summary
OutputStreamWriter(OutputStream out)
Creates an OutputStreamWriter that uses the default character encoding.
Creates an OutputStreamWriter that uses the default character encoding.
(三)IO 编程的一般流程:
1. 创建基本流
2. 升级基本流到高级流
3. 使用在高级流中的方法作读写操作
4. 关闭流并释放资源
-------------------------------------------------------------------------------
1. Creat node stream;
2. Upgrade node stream to processing stream if necessary
3. Use the methods in the stream object to read or write
4. Close the stream and release the resource
------------------------------------------------------------------------------
1. Create InputStream/Reader
2. Upgrade to Buffered
3. Use readLine()
While((str=in.readln())!=null)
4. close()
------------------------------------------------------------------------------
1. Create OutputStream/Writer
2. Upgrade to PrintWriter
3. Use println()
4. close()
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