package io;
import com.sun.istack.internal.NotNull;
import com.sun.istack.internal.Nullable;
import java.io.*;
import java.nio.charset.StandardCharsets;
public class iodemo {
public static void main(String[] args)throws IOException {
String src = "D:\\workspace\\javahmac\\leetcode\\io\\test1.txt";
String dest= "D:\\workspace\\javahmac\\leetcode\\io\\test2.txt";
// readThenWrite(src,dest);
bufferWrite(src,dest);
}
static String readMethod(@NotNull String path) throws IOException {
/** Return string */
InputStream in = new FileInputStream(path);
byte[] bytes = new byte[1024]; //todo onetime read bytes length !!!
int num=0;
// todo -1 表示文件指针到文件末尾，其他则返回num代表文件指针当前的位置，off表示byte 数组存放的偏移量
// read() * @返回读入缓冲区的字节总数，或者
// -1表示如果由于末尾没有更多数据，已到达流。
StringBuilder builder= new StringBuilder(); // String str="";也可以
while ((num=in.read(bytes,0,bytes.length))!=-1){
// str += new String(bytes, 0, num);也可以
builder.append(new String(bytes, 0, num)); // 一次转换多少字节为字符串,保留换行符等等
}
System.out.println(builder); // todo 带换行符号
return builder.toString();
}
@Deprecated
static void writeMethod(String path,@Nullable String mode,String text) throws IOException {
/** write bytes[] to file */
byte[] content = text.getBytes();
if(mode.equals("w")){
OutputStream out =new FileOutputStream(path,false); // w
out.write(content);
}
if(mode.equals("a")){
OutputStream out =new FileOutputStream(path,true); // true 追加写 a+
out.write(content);
}
}
/** onetime r onetime w */
static void readThenWrite(String src,String dest) throws IOException {
InputStream in = new FileInputStream(src); //todo append可以追加，如果dest不存在自动创建；
OutputStream out = new FileOutputStream(dest);
// todo 一次性取多少字节
byte[] bytes = new byte[1024];
//todo 文件指针-1表示最后一行
int num ;
while ((num = in.read(bytes,0,bytes.length)) != -1) {
//todo 一次转换每次读取的字节为string
String str = new String(bytes,0,num); //这里可以实现字节到字符串的转换，比较实用
System.out.println(str);
//todo 每次写入多少字节
out.write(bytes, 0, num);
}
//CLOSE STREAM
in.close();
out.close();
}
static String bufferRead(String src) throws FileNotFoundException,IOException {
//读取文件(缓存字节流)
BufferedInputStream in = new BufferedInputStream(new FileInputStream(src));
//todo 一次性取多少字节
byte[] bytes = new byte[2048];
//接受读取的内容(n就代表的相关数据，只不过是数字的形式)
int n = -1;
String str="";
while ((n = in.read(bytes,0,bytes.length)) != -1) {
//转换成字符串
str += new String(bytes,0,n);//charset utf-8 defaults
//System.out.println(str);
}
in.close();
return str.toString();
}
static void bufferWrite(String src,String dest) throws IOException {
//读取文件(缓存字节流)
BufferedInputStream in = new BufferedInputStream(new FileInputStream(src));
//写入相应的文件
BufferedOutputStream out = new BufferedOutputStream(new FileOutputStream(dest));
//一次性取多少字节
byte[] bytes = new byte[2048];
//接受读取的内容(n就代表的相关数据，只不过是数字的形式)
int n = -1;
//todo 循环取出数据,长度为bytes.length
while ((n = in.read(bytes,0,bytes.length)) != -1) {
//转换成字符串
String str = new String(bytes,0,n, StandardCharsets.UTF_8);
System.out.println(str);
//写入相关文件
out.write(bytes, 0, n);
}
//清除缓存
out.flush();
//关闭流
in.close();
out.close();
}
}