I/O流
程序员文章站
2022-06-13 22:22:48
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I/O流
Input output
输入输出
相对程序而言。Input认为read，output认为write。
文件—程序 input
程序—文件output
文件file类
2：流stream
字节流 用于读取图片，音视频等二进制文件
InputStream
outputStream
一个汉字 GBK里面占两个字节 UTF-8里面占三个字节
一个字符 GBK UTF-8占1个字节
总结：windows系统下的txt文档默认是ANSI编码是GBK，由于打开txt文档是记事本，所以写入txt文档内容时，记事本会“偷偷的”附加一些字节，使得原本录入的数据字节增大。Word更甚！本次使用IDE来完成txt文档纯净的字节录入，不被软件对录入内容附加格式干扰。
/**
*
*/
package com.zhiyou.S;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
/**
* @author Administrator
*
*/
public class InputStreamDemo {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
inputStreamDemo();
}
public static void inputStreamDemo() {
// 文件的输入流
// 创建文件的输入流对象，给定路径
try {
FileInputStream inputStream = new FileInputStream("D:\\a.txt");
// 新建一个字节数组，目的是存放读取过来的字节内容
byte[] fileByte = new byte[1024];
// 有可能产生I/O异常
inputStream.read(fileByte);
// 把字节数组转换成字符串
String string = new String(fileByte);
System.out.println(fileByte);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
// 如果文件是2000字节，byte数组是1024，会发生什么？
// 一次性只能读1024字节，读完肯定要执行多次的read操作。
// 每次可以记录读取的长度
// read方法返回值为-1代表已经读完。
// 尝试着让《三国》按照章节读取出来
}
/**
*
*/
package com.zhiyou.T;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.IOException;
/**
* @author Administrator
*
*/
public class InputSreamDemo {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
// read();
// read1();
// 缓冲区 无论读与写，先一次性塞满缓冲区再让缓冲区执行读与写，提升效率
// 直接进行的读写，是操作硬盘，缓冲区存放的是操作内容。
// cup与硬盘打交道远远低于CPU与内存的沟通
// BufferedInputStream
// BufferedOutputStream
// 对比fileInputStream和BufferedInputStream的执行效率
timeOfFileIputStream();
timeForBufferedInputStream();
// 从执行时间上来说bufferedInputStream要比FileInputStream快
}
public static void timeOfFileIputStream() {
// 获得1970.1.1到现在的毫秒数
long time1 = System.currentTimeMillis();
read1();
long time2 = System.currentTimeMillis();
System.out.println(time2 - time1);
}
public static void timeForBufferedInputStream() {
long time1 = System.currentTimeMillis();
read2();
long time2 = System.currentTimeMillis();
System.out.println(time2 - time1);
}
public static void read1() {
try {
FileInputStream inputStream = new FileInputStream("D:\\笔记\\总结.txt");
// 用已经创建的inputStream。转换成bufferedInputStream
// BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
byte[] bytes = new byte[1000];
int length = 0;
// while后面如果长度为-1就证明已经读完，就不在执行字符数组转换成字符串
while ((length = inputStream.read(bytes)) != -1) {
String string = new String(bytes, 0, length);
System.out.println(string);
}
inputStream.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void read2() {
try {
FileInputStream inputStream = new FileInputStream("D:\\笔记\\总结.txt");
// 用已经创建的inputStream。转换成bufferedInputStream
BufferedInputStream bufferedInputStream = new BufferedInputStream(inputStream);
byte[] bytes = new byte[1000];
int length = 0;
// while后面如果长度为-1就证明已经读完，就不在执行字符数组转换成字符串
while ((length = bufferedInputStream.read(bytes)) != -1) {
String string = new String(bytes, 0, length);
System.out.println(string);
}
bufferedInputStream.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void read() {
try {
FileInputStream inputStream = new FileInputStream("D:\\笔记\\总结.txt");
byte[] fileByte = new byte[1000];
int length = inputStream.read(fileByte);
System.out.println(length);
System.out.println(new String(fileByte));
System.out.println("1--------------------------------------");
int length1 = inputStream.read(fileByte);
System.err.println(length1);
System.out.println(new String(fileByte));
System.out.println("2-------------------------------------");
int length2 = inputStream.read(fileByte);
System.err.println(length2);
System.out.println(new String(fileByte));
System.out.println("3-------------------------------------");
int length3 = inputStream.read(fileByte);
System.err.println(length3);
System.out.println(new String(fileByte));
System.out.println("4-------------------------------------");
// read的结果代表是每次读字节的长度，-1代表读完
int length4 = inputStream.read(fileByte);
System.err.println(length4);
// 把字节数组从开始，转换length4长度的内容。
// fileByte
String string = new String(fileByte, 0, length4);
System.out.println(new String(fileByte));
System.out.println("5-------------------------------------");
inputStream.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
/**
*
*/
package com.zhiyou.T;
import java.io.BufferedOutputStream;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.OutputStream;
/**
* @author Administrator
*
*/
public class OutStremDemo {
/**
* @param args
*/
public static void main(String[] args) {
// TODO Auto-generated method stub
// fileOutputStream();
fileOutputStreamDemo();
}
public static void fileOutputStream() {
try {
FileOutputStream outputStream = new FileOutputStream("D:\\笔记\\2.txt");
String string = "老孙abc";
byte[] bytes = string.getBytes();
outputStream.write(bytes);
outputStream.close();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
public static void fileOutputStreamDemo() {
FileOutputStream outputStream = null;
BufferedOutputStream bufferedOutputStream = null;
try {
outputStream = new FileOutputStream("D:\\笔记\\2.txt");
bufferedOutputStream = new BufferedOutputStream(outputStream);
String string = "qwertyuiop";
byte[] bytes = string.getBytes();
bufferedOutputStream.write(bytes);
bufferedOutputStream.flush();
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} finally {
if (bufferedOutputStream != null) {
try {
bufferedOutputStream.close();
} catch (IOException e2) {
// TODO: handle exception
}
}
if (outputStream != null) {
try {
outputStream.close();
} catch (IOException e2) {
// TODO: handle exception
e2.printStackTrace();
}
}
}
}
}