How to copy a File or Directory in Java

In this article, you’ll learn how to copy a file or directory in Java using various methods like Files.copy() or using BufferedInputStream and BufferedOutputStream.

Tóm Tắt

Java Copy File using Files.copy()

Java NIO’s Files.copy() method is the simplest way of copying a file in Java.

import
 java
.
io.
IOException
;
import
 java
.
nio.
file.
*
;

public
 class
 CopyFileExample
 {
    public
 static
 void
 main
(
String
[
]
 args)
 {

        Path
 sourceFilePath =
 Paths
.
get
(
"./bar.txt"
)
;
        Path
 targetFilePath =
 Paths
.
get
(
System
.
getProperty
(
"user.home"
)
 +
 "/Desktop/bar-copy.txt"
)
;

        try
 {
            Files
.
copy
(
sourceFilePath,
 targetFilePath)
;
        }
 catch
 (
FileAlreadyExistsException
 ex)
 {
            System
.
out.
println
(
"File already exists"
)
;
        }
 catch
 (
IOException
 ex)
 {
            System
.
out.
format
(
"I/O error: %s%n"
,
 ex)
;
        }
    }
}

The Files.copy() method will throw FileAlreadyExistsException if the target file already exists. If you want to replace the target file then you can use the REPLACE_EXISTING option like this –

Files
.
copy
(
sourceFilePath,
 targetFilePath,
 StandardCopyOption
.
REPLACE_EXISTING)
;

Note that, Directories can be copied using the same method. However, files inside the directory are not copied, so the new directory will be empty even when the original directory contains files.

Java Copy File using BufferedInputStream and BufferedOutputStream

You can also copy a file byte-by-byte using a byte-stream I/O. The following example uses BufferedInputStream to read a file into a byte array and then write the byte array using BufferedOutputStream.

You can also use a FileInputStream and a FileOutputStream directly for performing the reading and writing. But a Buffered I/O is more performant because it buffers data and reads/writes it in chunks.

import
 java
.
io.
*
;
import
 java
.
nio.
file.
Files
;
import
 java
.
nio.
file.
Path
;
import
 java
.
nio.
file.
Paths
;

public
 class
 CopyFileExample1
 {
    public
 static
 void
 main
(
String
[
]
 args)
 {
        Path
 sourceFilePath =
 Paths
.
get
(
"./bar.txt"
)
;
        Path
 targetFilePath =
 Paths
.
get
(
System
.
getProperty
(
"user.home"
)
 +
 "/Desktop/bar-copy.txt"
)
;

        try
(
InputStream
 inputStream =
 Files
.
newInputStream
(
sourceFilePath)
;
            BufferedInputStream
 bufferedInputStream =
 new
 BufferedInputStream
(
inputStream)
;

            OutputStream
 outputStream =
 Files
.
newOutputStream
(
targetFilePath)
;
            BufferedOutputStream
 bufferedOutputStream =
 new
 BufferedOutputStream
(
outputStream)
)
 {

            byte
[
]
 buffer =
 new
 byte
[
4096
]
;
            int
 numBytes;
            while
 (
(
numBytes =
 bufferedInputStream.
read
(
buffer)
)
 !=
 -
1
)
 {
                bufferedOutputStream.
write
(
buffer,
 0
,
 numBytes)
;
            }
        }
 catch
 (
IOException
 ex)
 {
            System
.
out.
format
(
"I/O error: %s%n"
,
 ex)
;
        }
    }
}

Java Copy File using Files.copy()

Java Copy File using BufferedInputStream and BufferedOutputStream

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