Java Stream (i)

Flow :

Concept: The operation of a file in Java is done in a streaming fashion. A stream is an ordered set of data sequences in Java memory. Java reads the data from the source (file, memory, keyboard, network) into memory, forms a stream, and then writes those streams to another destination (file, memory, console, network), which is called a stream because the data sequence operates at different points in different parts of the source.

Understanding: A stream, can be seen as a pipe, the data used to read the file raw data are used in the form of binary data transmission

In/out Flow

Classification of streams

Follow the direction of the data flow

Input stream, output stream

Input stream: Move data from file to program

Output stream: From the program to the file to go data

The data is processed in different units:

The eight data types Occupy bytes:

BYTE (1), short (2), int (4), Long (8)

Float (4), double (8)

Boolean (1)

CHAR (2)

Byte stream (ends with stream), character stream (ends with reader, writer)

BYTE stream: 8 bits of bytes, read data in one byte

Character stream: Two bytes, one character per unit

According to the function of:

node flow, processing flow

Node stream: Only one root pipe sleeve is transferred on the file

Process flow: Process the node flow, enhance the function of the pipeline, equivalent to a layer on the pipe

The stream provided by the JDK

Provides four basic abstract classes: InputStream, OutputStream, Reader, Writer

Basic methods of InputStream:

int read (): Each time this method is called, a byte is read and returned as an integer

int read (byte[] buffer---buffer): Let the stream read one buffer at a time, and then unified processing, first exists in the buffer, the return value of int is to return the actual number of bytes read (the principle of damage to the hard disk)

int read (byte[] buffer, int offset, int length): is also a buffer that reads the number of bytes of length in buffer, which is saved from the offset position of buffer, and the return value is the actual number of words read Number of knots

Close (): Close Resource

Basic methods of OutputStream:

void write (int b)

void Write (byte[] b)

int Wirte (byte[] buffer, int offset, int length)

Close ()

Flush (): Writes out all the files in the buffer

In a good habit of using the flow, first flush, then close

Basic methods of Reader:

int read ()

int read (char[] c)

int read (char[] c, int offset, int length)

Close ()

Writer's basic methods:

void Write ()

void Write (char[] c)

void Write (char[] c, int offset, int length)

Write a string directly out, inside the string there is a method S.tochararray (), check API

void Write (String s)

void Write (String s, int offset, int length)

Close ()

Flush ()

BufferedReader

ReadLine ()---reads a row each time it is called

BufferedWriter

WriteLine (String s)---write one line per call

Java Stream (i)