java实现文件拷贝的七种方式
文章目录
- 1. 通过字节流实现文件的拷贝
- 2. 通过字符流实现文件拷贝
- 3. 通过字节缓冲流实现文件拷贝
- 4. 通过字符缓冲流拷贝文件
- 5. 通过JAVA NIO 非直接缓冲区拷贝文件
- 6. 通过JAVA NIO 直接缓冲区拷贝文件
- 7. 通过JAVA NIO 通道传输拷贝文件
- 使用示例
1. 通过字节流实现文件的拷贝
/**
* 通过字节流实现文件的拷贝
* @param sourcePath 源文件路径
* @param targetPath 目标文件路径
*/
public static void copyFileByStream(String sourcePath,String targetPath){
//源文件路径
File source = new File(sourcePath);
//目标文件路径
File target = new File(targetPath);
//如果源文件不存在则不能拷贝
if(!source.exists()){
return;
}
//如果目标文件目录不存在则创建
if(!target.getParentFile().exists()){
target.getParentFile().mkdirs();
}
try {
//实现文件的拷贝
InputStream inputStream = new FileInputStream(source);
OutputStream outputStream = new FileOutputStream(target);
int temp = 0;
//每次读取1024个字节
byte[] data = new byte[1024];
//将每次读取的数据保存到字节数组里面，并且返回读取的个数
while ((temp = inputStream.read(data)) != -1){
//输出数组
outputStream.write(data,0,temp);
}
inputStream.close();
outputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
2. 通过字符流实现文件拷贝
使用字符流只能拷贝文本文件
/**
* 通过字符流实现文件的拷贝
*
* @param sourcePath 源文件路径
* @param targetPath 目标文件路径
*/
public static void copyFileByReaderAndWriter(String sourcePath, String targetPath) {
//源文件路径
File source = new File(sourcePath);
//目标文件路径
File target = new File(targetPath);
//如果源文件不存在则不能拷贝
if (!source.exists()) {
return;
}
//如果目标文件目录不存在则创建
if (!target.getParentFile().exists()) {
target.getParentFile().mkdirs();
}
FileReader in = null;
FileWriter out = null;
try {
//字符输入流和字符输出流
in = new FileReader(source);
out = new FileWriter(target);
char[] c = new char[1024];
int temp = 0;
//每次读取1024个字符
while ((temp = in.read(c)) != -1) {
//输出到文件
out.write(c, 0, temp);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
//关闭流
try {
if (in != null) {
in.close();
}
if (out != null) {
out.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
3. 通过字节缓冲流实现文件拷贝
/**
* 通过字节缓冲流实现文件的拷贝
*
* @param sourcePath 源文件路径
* @param targetPath 目标文件路径
*/
public static void copyFileByBuffered(String sourcePath, String targetPath){
//源文件路径
File source = new File(sourcePath);
//目标文件路径
File target = new File(targetPath);
//如果源文件不存在则不能拷贝
if (!source.exists()) {
return;
}
//如果目标文件目录不存在则创建
if (!target.getParentFile().exists()) {
target.getParentFile().mkdirs();
}
InputStream in = null;
OutputStream out = null;
try {
//字节缓冲输入流和字节缓冲输出流
in = new BufferedInputStream(new FileInputStream(source));
out = new BufferedOutputStream(new FileOutputStream(target));
byte[] b = new byte[1024];
int temp = 0;
//每次读取一个1024的字节数组
while((temp = in.read(b)) != -1){
//输出到文件
out.write(b,0,temp);
}
} catch (Exception e) {
e.printStackTrace();
}finally {
//关闭流
try {
if (in != null) {
in.close();
}
if (out != null) {
out.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
4. 通过字符缓冲流拷贝文件
字符缓冲流只能读取文本文件
/**
* 通过字符缓冲流实现文件的拷贝
*
* @param sourcePath 源文件路径
* @param targetPath 目标文件路径
*/
public static void copyFileByBufferedChar(String sourcePath, String targetPath){
//源文件路径
File source = new File(sourcePath);
//目标文件路径
File target = new File(targetPath);
//如果源文件不存在则不能拷贝
if (!source.exists()) {
return;
}
//如果目标文件目录不存在则创建
if (!target.getParentFile().exists()) {
target.getParentFile().mkdirs();
}
BufferedReader in = null;
BufferedWriter out = null;
try {
//字符缓冲输入流和字符缓冲输出流
in = new BufferedReader(new FileReader(source));
out = new BufferedWriter(new FileWriter(target));
//读取文件（每次读取一行）
String temp = null;
while((temp = in.readLine()) != null){
//输出到文件
out.write(temp);
}
} catch (Exception e) {
e.printStackTrace();
}finally {
//关闭流
try {
if (in != null) {
in.close();
}
if (out != null) {
out.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
5. 通过JAVA NIO 非直接缓冲区拷贝文件
/**
* 通过JAVA NIO 非直接缓冲区拷贝文件
*
* @param sourcePath 源文件路径
* @param targetPath 目标文件路径
*/
public static void copyFileByChannel(String sourcePath, String targetPath) {
FileChannel outChannel = null;
FileChannel inChannel = null;
FileInputStream fis = null;
FileOutputStream fos = null;
try {
fis = new FileInputStream(sourcePath);
fos = new FileOutputStream(targetPath);
//获取通道
inChannel = fis.getChannel();
outChannel = fos.getChannel();
//分配指定大小的缓冲区
ByteBuffer buf = ByteBuffer.allocate(1024);
while (inChannel.read(buf) != -1) {
//转换为读取数据模式
buf.flip();
//写入到磁盘
outChannel.write(buf);
//清空缓冲区
buf.clear();
}
} catch (Exception e) {
e.printStackTrace();
} finally {
//关闭流
try {
if (outChannel != null) {
outChannel.close();
}
if (inChannel != null) {
inChannel.close();
}
if (fis != null) {
fis.close();
}
if (fos != null) {
fos.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
6. 通过JAVA NIO 直接缓冲区拷贝文件
/**
* 通过JAVA NIO 直接缓冲区拷贝文件（内存映射文件）
*
* @param sourcePath 源文件路径
* @param targetPath 目标文件路径
*/
public static void copyFileByChannelBufferd(String sourcePath, String targetPath) {
FileChannel inChannel = null;
FileChannel outChannel = null;
try {
//获取通道,StandardOpenOption.READ表示可读，StandardOpenOption.WRITE表示可写，StandardOpenOption.CREATE表示可以创建
inChannel = FileChannel.open(Paths.get(sourcePath), StandardOpenOption.READ);
outChannel = FileChannel.open(Paths.get(targetPath), StandardOpenOption.WRITE, StandardOpenOption.READ, StandardOpenOption.CREATE);
//创建内存映射文件
MappedByteBuffer inMapped = inChannel.map(FileChannel.MapMode.READ_ONLY, 0, inChannel.size());
MappedByteBuffer outMapped = outChannel.map(FileChannel.MapMode.READ_WRITE, 0, inChannel.size());
//直接操作内存映射文件
byte[] buf = new byte[inMapped.limit()];
inMapped.get(buf);
outMapped.put(buf);
} catch (IOException e) {
e.printStackTrace();
} finally {
//关闭流
try {
if (outChannel != null) {
outChannel.close();
}
if (inChannel != null) {
inChannel.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
7. 通过JAVA NIO 通道传输拷贝文件
方式一
/**
* 通过JAVA NIO 通道传输拷贝文件
*
* @param sourcePath 源文件路径
* @param targetPath 目标文件路径
*/
public static void copyFileByChannelTransfer(String sourcePath, String targetPath) {
FileChannel inChannel = null;
FileChannel outChannel = null;
try {
//获取通道
inChannel = FileChannel.open(Paths.get(sourcePath), StandardOpenOption.READ);
outChannel = FileChannel.open(Paths.get(targetPath),StandardOpenOption.WRITE,StandardOpenOption.READ,StandardOpenOption.CREATE);
inChannel.transferTo(0,inChannel.size(),outChannel);
} catch (IOException e) {
e.printStackTrace();
}finally {
//关闭流
try {
if (outChannel != null) {
outChannel.close();
}
if (inChannel != null) {
inChannel.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
方式二
/**
* 通过JAVA NIO 通道传输拷贝文件
*
* @param sourcePath 源文件路径
* @param targetPath 目标文件路径
*/
public static void copyFileByChannelTransfer2(String sourcePath, String targetPath) {
FileInputStream fis = null;
FileOutputStream fos = null;
FileChannel inChannel = null;
FileChannel outChannel = null;
try {
fis = new FileInputStream(sourcePath);
fos = new FileOutputStream(targetPath);
//获取通道
inChannel = fis.getChannel();
outChannel = fos.getChannel();
inChannel.transferTo(0,inChannel.size(),outChannel);
} catch (IOException e) {
e.printStackTrace();
}finally {
//关闭流
try {
if (outChannel != null) {
outChannel.close();
}
if (inChannel != null) {
inChannel.close();
}
} catch (IOException e) {
e.printStackTrace();
}
}
}
使用示例
String source = "e:\\demo\\纵天神帝.txt";
String target = "e:\\demo\\";
long time1 = System.currentTimeMillis();
copyFileByStream(source, target + "1.txt");
System.out.println("通过字节流实现文件的拷贝耗时：" + (System.currentTimeMillis() - time1));
long time2 = System.currentTimeMillis();
copyFileByReaderAndWriter(source, target + "2.txt");
System.out.println("通过字符流实现文件的拷贝耗时：" + (System.currentTimeMillis() - time2));
long time3 = System.currentTimeMillis();
copyFileByBuffered(source, target + "3.txt");
System.out.println("通过字节缓冲流实现文件的拷贝耗时：" + (System.currentTimeMillis() - time3));
long time4 = System.currentTimeMillis();
copyFileByBufferedChar(source, target + "4.txt");
System.out.println("通过字符缓冲流实现文件的拷贝耗时：" + (System.currentTimeMillis() - time4));
long time5 = System.currentTimeMillis();
copyFileByChannel(source, target + "5.txt");
System.out.println("通过JAVA NIO通道（非直接缓冲区）实现文件的拷贝耗时：" + (System.currentTimeMillis() - time5));
long time6 = System.currentTimeMillis();
copyFileByChannelBufferd(source, target + "6.txt");
System.out.println("通过JAVA NIO通道（直接缓冲区）实现文件的拷贝耗时：" + (System.currentTimeMillis() - time6));
long time7 = System.currentTimeMillis();
copyFileByChannelTransfer(source, target + "7.txt");
System.out.println("通过JAVA NIO通道传输实现文件的拷贝耗时：" + (System.currentTimeMillis() - time7));
long time8 = System.currentTimeMillis();
copyFileByChannelTransfer(source, target + "8.txt");
System.out.println("通过JAVA NIO通道传输2实现文件的拷贝耗时：" + (System.currentTimeMillis() - time8));
通过测试发现，使用JAVA NIO通道传输、JAVA NIO通道直接缓冲区以及字节缓冲流拷贝文件效率最高