Java IO

创建: 2020/11/22

完成: 2020/11/22 

https://docs.oracle.com/javase/7/docs/api/java/io/package-summary.html

 

File  

 构造函数

 

File(String path)
File(String directoryPath, String filename)
File(File directory, String filename)
File(URI uri)	path为空抛出NullPointerException

 静态变量

 

static String pathSeparator static char pathSeparatorChar	路径分隔符
static String separator static char separatorChar	文件分割符

实例方法

 

判断

boolean canExecute()	存在且运行
boolean canRead()
boolean canWrite()
boolean exists()
boolean isAbsolute()	path是否是绝对路径
boolean isDirectory()
boolean isFile()
boolean isHidden()

获取

String getAbsolutePath()	绝对路径
String getCanonicalPath() throws IOException	标准路径
long getFreeSpace()	文件系统剩余的容量 单位: 字节(byte)
long getTotalSpace()
long getUsedSpace()
String getName()	文件名
String getParent()
String getPath()
long lastModified()	1970/1/1GMT到最后更改直接的毫秒
long length()	文件大小 单位: byte
String[] list() String[] list(FilenameFilter filter)	返回文件夹内的文件
File[] list() File[] list(FilenameFilter filter)

设置

boolean setExecutable(boolean flag, boolean owner)	owner: true 只有onwer 　　　　false All 成功返回true
boolean setReadable(boolean flag, boolean owner)
boolean setWritable(boolean flag, boolean owner)
boolean setLastModified(long t)
URI toURI()	返回 file:// 开头的URI

boolean createNewFile()

throws IOException

创建新的空文件, 成功返回true

boolean delete()

删除文件。成功返回true

boolean mkdir()

以此文件名创建新文件夹

• 上层文件夹必须都存在

boolean mkdirs()

以此文件名创建新文件夹

• 上层文件夹不存在就一并创建

boolean renameTo(File newName)

成功返回true

字符流

简介

• 两种流, 字符流(charactor stream), 字节流(byte stream)

字符流类关系图 

 继承关系图

		BufferdReader
	Reader ->
		InputStreamReader ->	FileReader
Object ->
		BufferdWriter
	Writer ->	OutputStreamWriter ->	FileWriter
		PrintWriter

 

 

 

Writer

 

 

这是抽象类

 

构造函数

Writer()
Writer(Object obj)

实例函数

append

Writer append(char c) throws IOException
Writer append(CharSequence cs) throws IOException
Writer append(CharSequence cs, int strat, int end) throws IOException	写入cs里指定范围的部分到流

write

void write(int c) throws IOException
void write(char buffer[]) throws IOException
abstract void write(char buffer[], int index, int size) throws IOExceptio	index写入流起始位置(流的) size写入的字符数
void write(String s) throws IOException
void write(String s, int index, int size) throws IOException

abstract void close()

throws IOException

abstract void flush()

throws IOException

写入终端

OutputStreamWriter

 

简介

Object -> Writer -> OutputStreamWriter

字符流转换为字节流输出到终端

构造函数

OutputStreamWriter(OutputStream os)	不指定encoding则使用系统默认
OutputStreamWriter(OutputStream os, String encoding)

实例方法

String getEncoding()

 FileWriter

 

简介

Object -> Writer -> OutputStreamWriter -> FileWriter

向文件输出

构造函数

FileWriter(String filepath) throws IOException
FileWriter(String filepath, boolean append) throws IOException
FileWriter(File fileObj) throws IOException
FIleWriter(File fileObj, boolean append) throws IOException	append: true则在末尾添加, false则删除原内容

没有自己的函数, 全是继承的

Reader

 

 

 

 

这是抽象类

构造函数

Reader()
Reader(Object obj)

实力函数

abstract void close() throws IOException

关闭读取流, 再尝试读取则抛出IOException

void mark(int numChars) throws IOException

???

void reset() throws IOExceptio 

int skip(long numChars) throws IOException

返回实际跳过的数量

read

int read() throws IOException	读取的是一个字符
int read(char buffer[]) throws IOException
abstract int read(char buffer[], int offset, int numChars) throws IOException

判断

boolean markSupported()	此流是否支持mark()/reset()
boolean ready() throws IOException	read不在读取返回true

InputStreamReader

 

简介

Object -> Reader -> InputStreamReader

字节流读取为字符流

构造函数

InputStreamReader(InputStream is)
InputSreamReader(IntputSream is, String encoding)

实例函数

String getEncoding()

FileReader

 

简介

Object -> Reader -> InputStreamReader -> FileReader

构造函数

FileReader(String filepath) throws FileNotFoundException
FileReader(File fileObj) throws FileNotFoundException

没有自己的函数, 全是继承的

带buffer字符流

 简介

 写入和读取都存到buffer里

 好处: 减少直接写入和读取的次数, 提高performance

BufferedWriter

 

简介

Objcet -> Writer -> BufferedWriter

构造函数

BuffferedWriter(Writer w)
BufferedWriter(Writer w, int bufSize)

实例函数

void newLine() throws IOException()

写入一个换行(另起一行)

BufferedReader 

 

简介

Object -> Reader -> BufferedReader

构造函数

BufferedReader(Reader r)
BufferedReader(Reader r, int bufSize)

实例函数

String readLine() throws IOException

PrintWriter

 Object -> Writer -> PrintWriter

构造函数

 

PrintWriter(File fileObj) throws FileNotFoundException
PrintWriter(OutputStream os)
PrintWriter(OutputStream os, boolean flushOnNewline)
PrintWriter(Writer writer)
PrintWriter(Writer writer, boolean flushOnNewline)

实例方法

 

print

void pirnt(boolean b)
void print(char c)
void print(char cs[])
void print(double d)
void print(float f)
void print(int i)
void print(long l)
void print(Object o)
void print(String s)

println

void println()
其他9个和print一样

printf

void printf(String s, Object... args) void format(String s, Object... args)
void printf(Locale l, String s, Object... args) void format(Locale l, String s, Object... args)

字节流

字节流类关系图 

继承关系图

		FileInputStream
	InputStream ->		BufferedInputStream
		FilterInputStream ->	DataInputStream
Object ->
		FileOutputStream
	OutputStream ->		BufferedOutputStream
		FilterOutputStream ->	DataOutputStream
			PrintStream

OutputStream 

 这是抽象类

简介

Object -> OutputStream

构造函数

OutoutStream()

实例方法

void close() throws IOException

void flush() throws IOException

write

abstract void write(int i) throws IOException
void write(byte buffer[]) throws IOException
void write(byte buffer[], int index int size) throws IOException	把size数量的buffer字符写入index处

FileOutputStream

 

简介

Object -> OutputStream -> FileOutputStream

构造函数

FileOutputStream(String filepath) throws FileNotFoundException
FIleOutputStream(String filepath, boolean append) throws FileNotFoundException
FileOutputStream(File fileObj) throws FileNotFoundException
FileOutputStream(File fileObj, boolean append) throws FileNotFoundException

FilterOutpuStream

 

简介

Object -> OutputStream -> FilterOutputStream

用filter过滤后再输出

构造函数

FilterOutputStream(OutputStream os)

BufferedOutputStream

 

简介

Object -> OutputStream -> FilterOutputStream -> BufferedOutputStream

构造函数

BufferedOutputStream(OutputStream os)
BufferedOutputStream(OutputStream os, int bufSize)

DataOutputStream

 

简介

Object -> OutputStream -> FilterOutputStream -> DataOutputStream

能把基本数据类型直接写入的

构造函数

DataOutputStream(OutputStream os)

实例函数

write

void write(int i) throws IOException
void witer(byte buffer[]) throws IOException
void write(byte buffer[], int index, int size) throws IOException
…………………分割线………………
void writeBoolean(boolean b) throws IOException
void writeByte(int i) throws IOException void writeChar(int i) throws IOException
void writeBytes(Strings) throws IOException void writeChars(String s) throws IOException
void writeDouble(double d) throws IOException
void writeFloat(float f) throws IOException
void writeInt(int i) throws IOException
void writeLong(long l) throws IOException
void writeShort(short s) throws IOException
void writeUTF(String s) throws IOException	把字符串转换从Unicode转为UTF-8再写入

PrintStream

简介

Object -> OutputStream -> FilterOutputStream -> PrintStream

构造函数

PrintStream(File fileObj) throws FileNotFoundException
PrintStream(String filepath) throws FileNotFoundException
PrintStream(OutputStream os)
PrintStream(OutputStream os, boolean flushOnNewLine)

实例方法

printf

printf(String format, Object... args) format(String format, Object... args)
printf(Locale l, String format, Object... args) format(Locale l, String format, Object... args)

 InputStream

 这是抽象类

构造函数

InputStream()

实例方法

 

int available() throws IOException

返回现在读取可用的字节数byte

void close() throws IOexception

void mark(int numBytes)

void reset() throws IOException

int skip(long numBytes) throws IOException

跳过指定byte数, 返回实际跳过的byte数

boolean markSupported()

是否支持mark()/reset()

read

int read() throws IOException	读1byte
int read(byte buffer[]) throws IOException	读buffer.length长度
int read(byte buffer[], int offset, int numBytes) throws IOException	返回实际读取数 offset: 存入的起始位置 numBytes: 尝试读取数

FileInputStream

 

简介

Object -> InputStream -> FileInputStream

构造函数

FileInputStream(String filepath) throws FileNotFountException
FileInputStream(File fileObj) throws FileNotFoundException

FilterInputStream 

 

简介

Object -> InputStream -> FilterInputStream

构造函数

FilterInputStream(InputStream is)

BufferedInputStream

简介

Object -> InputStream -> FilterInputStream -> BufferedInputStream

构造函数

 

BufferedInputStream(InputStream is)
BufferedInputStream(InputStream is, int bufSize)

 

DataInputStream

简介

Object -> InputStream -> FilterInputStream -> DataInputStream

构造函数

DataInputStream(InputStream is)

实例函数

read
int skipBytes(int n) throws IOException	跳过n字节, 返回实际跳过的

随机接入文件

简介

可以在文件内随意读取写入

Object -> RandomAccessFile

https://docs.oracle.com/javase/7/docs/api/java/io/RandomAccessFile.html

构造函数

 

RandomAccessFile(String filepath, String mode) throws FileNotFoundException RandomAccessFile(File fileobj, String mode) throws FileNotFoundException

mode: r, rw, rws, rwd

实例方法

 

void close() throws IOException

long getFilePointer() throws IOException

long length() throws IOException

返回文件的byte数

read

int read() throws IOException	读取一字节
int read(byte buffer[], int index, int size) throws IOException	返回实际读取的字节数
int read(byte buffer[]) throws IOException

void seek(long n) throws IOException

指针指向开头起n的位置

void setLength(long size) throws IOException

int skipBytes(int n) throws IOException

StreamTokenizer

构造函数 

 

StreamTokenizer(Reader r)

实例函数 

 

void commentChar(int ch)

指定ch是单行注释的开始

void eollsSignificant(boolean flag)

true: 行末作为token

flase: 作为空白

int lineno()

void lowerCaseMode(boolean flag)

true: 把文字自动转为小写

int nextToken() throws IOException

数字返回TT_NUMBER

单词返回TT_WORD

其他则返回相同的字符

ordinaryChar

void ordinaryChar(int ch)
void ordinaryChar(int c1, int c2)

void parseNumbers()

void pushBacK()

void quoteChar(int ch)

void resetSyntax()

void slashSlashComments(boolean flag)

void slashStraComments(boolean flag)

String toString()

void whiteSpaceChars(int c1, int c2)

void wordChars(int c1, int c2)