java 写入磁盘 java nio写入文件

java NIO方式进行读写文件和内容
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.MappedByteBuffer;
import java.nio.channels.FileChannel;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
/**
*
* 测试JAVA NIO方式读取文件，写出内容到文件
*
*/
public class NIOTest {
public static void main(String[] args) {
readNIO();
}
/**
* 最终确认，是因为UTF-8编码的时候，是变长的(可能1-4个字节)，所以在
* ByteBuffer bf = ByteBuffer.allocate(capacity);
* byte[] bytes = bf.array();
* 的时候，会出现数字英文和中文边界截断了的问题，所以导致出现测���java 文件操作这样的乱码。
* 解决方案1：对这类文件不进行截断输出，整个输出
* 解决方案2：截断输出的时候，判断编码边界。进行减长度操作，避免截断了中文。
*/
public static void readNIO() {
FileInputStream fin = null;
try {
fin = new FileInputStream(new File("D:\\add0.txt"));
FileChannel channel = fin.getChannel();
int capacity = 1024;// 字节
ByteBuffer bf = ByteBuffer.allocate(capacity);
System.out.println("限制是：" + bf.limit() + ",容量是：" + bf.capacity() + " ,位置是：" + bf.position());
int length = -1;
while ((length = channel.read(bf)) != -1) {
/*
* 注意，读取后，将位置置为0，将limit置为容量, 以备下次读入到字节缓冲中，从0开始存储
*/
bf.clear();
byte[] bytes = bf.array();
//System.out.println("start..............");
最后输出就会有乱码符号：测���java 文件操作这样输出也有乱码
String str = new String(bytes, 0, length,"UTF-8");
System.out.println(str);
//System.out.write(bytes, 0, length);
//System.out.println("end................");
System.out.println("限制是：" + bf.limit() + "容量是：" + bf.capacity() + "位置是：" + bf.position());
}
//最后输出就会有乱码符号：测���java 文件操作
//System.out.println(str);
channel.close();
} catch (FileNotFoundException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} finally {
if (fin != null) {
try {
fin.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
/**通道之间的数据传输(直接缓冲区的模式)
* 耗费时间:68
*
*/
private static void nioCopyTest3() throws IOException {
long startTime = System.currentTimeMillis();
FileChannel inChannel = FileChannel.open(Paths.get("E:\\ 1.avi"), StandardOpenOption.READ);
FileChannel outChennel = FileChannel.open(Paths.get("E:\\ 13.avi"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW);
outChennel.transferFrom(inChannel,0,inChannel.size());
long end = System.currentTimeMillis();
System.out.println("nioCopyTest3耗费时间:"+(end-startTime));
}
/**
* 使用直接缓冲区完成文件的复制(内存映射文件)
* 耗费时间:142
*/
private static void nioCopyTest2() throws IOException {
long startTime = System.currentTimeMillis();
FileChannel inChannel = FileChannel.open(Paths.get("E:\\ 1.avi"), StandardOpenOption.READ);
FileChannel outChennel = FileChannel.open(Paths.get("E:\\ 12.avi"),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE_NEW);
//内存映射文件(什么模式 从哪开始 到哪结束)
MappedByteBuffer inMappeBuf = inChannel.map(FileChannel.MapMode.READ_ONLY,0,inChannel.size());
MappedByteBuffer outMappeBuf = outChennel.map(FileChannel.MapMode.READ_WRITE,0,inChannel.size());
//直接都缓冲区进行数据的读写操作
byte[] dst = new byte[inMappeBuf.limit()];
inMappeBuf.get(dst);
outMappeBuf.put(dst);
inChannel.close();
outChennel.close();
long end = System.currentTimeMillis();
System.out.println("nioCopyTest2耗费时间:"+(end-startTime));
}
/**
* 非直接缓冲区 文件的复制
* 耗费时间:1417
* @throws IOException
*/
private static void nioCopyTest1()throws IOException {
long startTime = System.currentTimeMillis();
FileInputStream fileInputStream = new FileInputStream(new File("E:\\ 1.avi"));
FileOutputStream fileOutputStream = new FileOutputStream("E:\\ 11.avi");
//获取通道
FileChannel inChannel = fileInputStream.getChannel();
FileChannel outChanel = fileOutputStream.getChannel();
//分配缓冲区的大小
ByteBuffer buf = ByteBuffer.allocate(1024);
//将通道中的数据存入缓冲区
while (inChannel.read(buf) != -1) {
buf.flip();//切换读取数据的模式
outChanel.write(buf);
buf.clear();
}
outChanel.close();
inChannel.close();
fileInputStream.close();
fileOutputStream.close();
long end = System.currentTimeMillis();
System.out.println("nioCopyTest1耗费时间:"+(end-startTime));
}
}