day13
I/O流
定义：数据在两设备传输称为流，流是一组有顺序的，有起点和终点的字节集合
I 是input的缩写，表示输入流
O是output缩写，表示输出流
字节流（视频等）
输入InputStream FileInputStream DataInputStream
输出OutputStream FileOutputStream DataOutputStream
public static void main(String[] args){
try{
inputData();//调用字节输入流
}catch(IOException e){
e.printStackTrace();
}
}
//===========字节流==========
//-----------字节输入流-------
public static void inputData() throws IOException{
//1.创建file对象，加载文件物理路径
File file = new File("D://siTu/测试.txt");
//2.创建字节输入流
InputStream in = new FileInputStream(file);
//3.返回字节输入流的刻度字节长度
int len = in.available();
/**全英文文档
for(int i = 0; i < size; i++){
char c = (char)in.read();//in.read()返回ascii码的十进制数
//read（）返回的是ascii码的十进制数，每个数字对应一个字符
}
*/
/**含中文文档
先创建一个byte数组用于接收读取的内容
for循环把读取的数据全都强转后放在byte数组中
输出一个byte数组转成的字符串，从而处理中文
*/
byte[] b = new byte[len];
for(int i = 0; i < b.length; i++){
b[i] = (byte)in.read();
}
System.out.println(new String(b));
}
//-----------字节输出流—-----------
public static void outputStream{
//新建文件对象，并且获取物理地址
File file = new File(D://siTu/测试.txt);
//输入需要添加的字符
String str = "元气";
//创建字节输出流FileOutputStream(File file, boolean append)是否在file文件后拼接，true拼接
OutputStream out = new FileOutputStream(file,true);
//OutputStream out = new FileOutputStream(file);
out.write(out.getByte());//把字符串转化成字节数组后 再写入文件
out.flush();
out.close();
}
字符流(文档)
输入 Reader FileReader
BufferedReader
输出 Writer FileWriter
BufferedReader
字符输入流读文件
//===========字符流==========
//-----------字符输入流-------
public static void OutputDate(){
File file = new File("D://siTu/测试.txt");
InputStream inp = new InputStream(file);
InputSteramReader reader = new InputStreamReader(inp,"UTF-8");
BufferedReader br = new BufferedReader(reader);
/**
String str = null;
while((str = br.readLine()) != null){
System.out.println(str);
}
*/
byte[] bt = new byte[1024];
/*
int len = in.read(bt);//每次读取指定数组长的字节数，并将读到的字节传入大数组中，返回读到的字节长度
while(len != -1){
out.write(bt);
len = in.read(bt);
}
*/
int len = -1;
while((len = in.read(bt)) != -1){
out.write(bt);
}
out.close();
in.close();
}
字符输出流
//-----------字符输出流-------
public static void outputreader(){
File file = new File("D://siTu/测试1.txt");
String str = "zg";
OutputStream out = null;
OutputStreamWriter writer = null;
BufferedWriter bw = null;
try{
out = new OutputStream(file,true);
writer = new OutputStreamWriter(out,"UTF-8");
bw = new BufferedWriter(writer);
bw.write("1111");
bw.newLine();
bw.write("aaaa");
bw.flush();
}catch(IOException e){
e.printStrackTrace();
}finally{
(try catch)if(bw != null) bw.close();
(try catch)if(writer != null) writer.close();
(try catch)if(out != null) out.close();
}
}
File类常用的方法
File file = new File("D://siTu/ceshi.txt");
1.文件是否存在
boolean has = file.exists();
2.是否是 一个文件
boolean b = file.isFile();
3.判断是否是一个文件夹（目录）
boolean b1 = file.isDirectory();
4.获取当前目录下所有文件名
String[] fileNames = file.list();
5.获取当前目录下所有文件对象
File[] files = file.listFiles();
6.删除文件或者文件夹(boolean)
file.delete();
7.当文件，文件夹存在时，执行删除
file.deleteOnExit();
8.创建文件夹boolean
file.mkdir();
9.获取文件名
String name = file.getName();
10.创建新的文件
try {
boolean tar2 = file.createNewFile();
System.out.println(tar2);
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
11.判断一个文件是否可读boolean
file.canRead();
12.判断一个文件是否可写boolean
file.canWrite();
复制大文件
public static void copy(){
InputStream in = new FileInputStream(new File("D://siTu/测试2.txt"));
OutputStream out = new FileOutputStream(new File("D://siTu/测试22.txt"));
/** int len = in.available();
syso(len);
for(int i = 0; i < len ; i++){
out.write(in.read);
}
out.close();
*/
/**
byte[] bt = new byte[1024];
int len = in.read(bt);
while(len != -1){
out.write(bt);
len = in.read(bt);
}
out.close();
in.close();
*/
byte[] bt = new byte[1024];
int len = -1
while((len = in.read(bt) != -1){
out.write(bt);
}
out.close();
in.close();
}