java實現檔案拷貝的幾種方式（全！！）
阿新 • • 發佈：2019-03-05
一、前言：下面例子中，所有異常處理均採用丟擲的形式，各位千萬不要效仿
二、幾種拷貝檔案的方式
2.1 位元組流的形式
public static void byteCopy(String sourcePath,String target) throws IOException { //1.建立輸入流 InputStream iStream = new FileInputStream(sourcePath); //2.建立輸出流 OutputStream oStream = new FileOutputStream(target); //3.一部分一部分讀出 byte[] bytes = new byte[10*1024]; int br;//實際的讀取長度 while((br =iStream.read(bytes))!=-1) {//判斷是否讀到末尾 oStream.write(bytes, 0, br); } //4.清空快取 oStream.flush(); //5.關閉流 if(iStream!=null) { iStream.close(); } if(oStream!=null) { oStream.close(); } }
2.2 位元組流一次複製完成，缺點是：只能應用於小檔案
public static void byteCopy2(String sourcePath,String target) throws IOException { //1.建立輸入流 InputStream iStream = new FileInputStream(sourcePath); //2.建立輸出流 OutputStream oStream = new FileOutputStream(target); int len = iStream.available(); //3.全部讀出 byte[] bytes = new byte[len]; iStream.read(bytes); oStream.write(bytes, 0, len); //4.清空快取 oStream.flush(); //5.關閉流 if(iStream!=null) { iStream.close(); } if(oStream!=null) { oStream.close(); } }
2.3 帶緩衝的位元組流
public static void byteCopy3(String sourcePath,String target) throws IOException { //1.建立輸入流 BufferedInputStream bufferedInputStream = new BufferedInputStream(new FileInputStream(sourcePath)); //2.建立輸出流 BufferedOutputStream bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(target),1024*1024); //3.一部分一部分讀出 byte[] bytes = new byte[10*1024]; int br;//實際的讀取長度 while((br =bufferedInputStream.read(bytes))!=-1) {//判斷是否讀到末尾 bufferedOutputStream.write(bytes, 0, br); } //4.清空快取 bufferedOutputStream.flush(); //5.關閉流 if(bufferedInputStream!=null) { bufferedInputStream.close(); } if(bufferedOutputStream!=null) { bufferedOutputStream.close(); } }
2.4 字元流完成，缺點：不能指定字符集，不建議使用
public static void CharCopy(String sourcePath,String target) throws IOException{
Reader reader = new FileReader(sourcePath);
Writer writer = new FileWriter(target);
char[] c = new char[10];
int read;
while((read = reader.read(c))!=-1) {
writer.write(c, 0, read);
}
writer.flush();
if(reader!=null) {
reader.close();
}
if(writer!=null) {
writer.close();
}
}2.5 標準的字元流實現，能指定字符集，一行一行讀出，true表示追加
public static void CharCopy2(String sourcePath,String target) throws IOException{
BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(new FileInputStream(sourcePath), "utf-8"));
PrintWriter printWriter = new PrintWriter(new OutputStreamWriter(new FileOutputStream(target,true),"utf-8"));
String line;
while((line = bufferedReader.readLine())!=null) {
printWriter.write(line+"\n");
}
if(bufferedReader != null) {
bufferedReader.close();
}
if(printWriter != null) {
printWriter.close();
}
}2.6 NIO實現檔案拷貝（用transferTo的實現 或者transferFrom的實現），這裡是transferTo的實現。
public static void NIOCopyFile(String source,String target) throws Exception{
//1.採用RandomAccessFile雙向通道完成，rw表示具有讀寫許可權
RandomAccessFile fromFile = new RandomAccessFile(source,"rw");
FileChannel fromChannel = fromFile.getChannel();
RandomAccessFile toFile = new RandomAccessFile(target,"rw");
FileChannel toChannel = toFile.getChannel();
long count = fromChannel.size();
while (count > 0) {
long transferred = fromChannel.transferTo(fromChannel.position(), count, toChannel);
count -= transferred;
}
if(fromFile!=null) {
fromFile.close();
}
if(fromChannel!=null) {
fromChannel.close();
}
}2.7 NIO實現檔案自身內容拷貝（追加到末尾）
public static void main(String[] args) throws Exception {
//1.獲取雙向通道
RandomAccessFile file = new RandomAccessFile("C:\\Users\\num11\\Desktop\\grade.txt","rw");
//2.得到通道
FileChannel channel = file.getChannel();
//3.定義快取
ByteBuffer byteBuffer = ByteBuffer.allocate(1024);
if(channel.read(byteBuffer)!= -1){ //判斷是否讀到末尾
//4.反轉
byteBuffer.flip();
channel.write(byteBuffer);
byteBuffer.clear();
}
if(file != null){
file.close();
}
}2.8 java.nio.file.Files.copy()實現檔案拷貝，其中第三個引數決定是否覆蓋
public static void copyFile(String source,String target){
Path sourcePath = Paths.get(source);
Path destinationPath = Paths.get(target);
try {
Files.copy(sourcePath, destinationPath,
StandardCopyOption.REPLACE_EXISTING);
} catch (IOException e) {
//something else went wrong
e.printStackTrace();
}
}