In Java, we can use the following two Files.createTempFile() methods to create a temporary file in the default temporary-file directory.
Path createTempFile(Path dir,
String prefix,
String suffix,
FileAttribute<?>... attrs) throws IOException
Path createTempFile(String prefix,
String suffix,
FileAttribute<?>... attrs) throws IOException
The default temporary file folder is vary on operating system.
- Windows –
%USER%\AppData\Local\Temp - Linux –
/tmp
1. Create Temporary Files
1.1 This example uses Files.createTempFile(prefix, suffix) to create a temporary file. If the suffix is null, the default is .tmp.
CreateTempFile.java
package com.favtuts.io.temp;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
public class CreateTempFile {
public static void main(String[] args) {
String tmpdir = System.getProperty("java.io.tmpdir");
System.out.println("Temp file path: " + tmpdir);
try {
// Create an temporary file
Path temp = Files.createTempFile("hello", ".file");
System.out.println("Temp file : " + temp);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output
Temp file path: /tmp
Temp file : /tmp/hello16199335803757730781.file1.2 prefix = null, suffix = “.log”
Path temp = Files.createTempFile(null, ".log");
System.out.println("Temp file : " + temp);
// Temp file : /tmp/1293798546881960950.log1.3 prefix = “hello”, suffix = null
Path temp = Files.createTempFile("hello", null);
System.out.println("Temp file : " + temp);
// Temp file : /tmp/hello14667182763055433377.tmp1.4 prefix = “hello”, suffix = “”
Path temp = Files.createTempFile("hello", "");
System.out.println("Temp file : " + temp);
// Temp file : /tmp/hello132579231221758396191.5 prefix = null, suffix = null
Path temp = Files.createTempFile(null, null);
System.out.println("Temp file : " + temp);
// Temp file : /tmp/6253298279510303633.tmp2. Create Temporary Files in a specified directory
2.1 In Java, we can pass a java.nio.file.Path to Files.createTempFile to create a temporary file in a specified directory.
CreateTempFile2.java
package com.favtuts.io.temp;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
public class CreateTempFile2 {
public static void main(String[] args) {
try {
Path path = Paths.get("/home/tvt/workspace/favtuts/temp/");
// Create an temporary file in a specified directory.
Path temp = Files.createTempFile(path, null, ".log");
System.out.println("Temp file : " + temp);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output
Temp file : /home/tvt/workspace/favtuts/temp/4632902976799078765.logIf the specified folder does not exist, Java throws NoSuchFileException.
java.nio.file.NoSuchFileException: /home/tvt/workspace/favtuts/temp/8813322845011292158.log3. Create Temporary Files + File Permission
3.1 This example tries to assign 777 file permission during temporary file creation.
CreateTempFile3.java
package com.favtuts.io.temp;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.attribute.PosixFilePermission;
import java.nio.file.attribute.PosixFilePermissions;
import java.util.Set;
public class CreateTempFile3 {
public static void main(String[] args) {
try {
// Create a temporary file in a specified folder + file permission
Path path = Paths.get("/home/tvt/workspace/favtuts/temp/");
// 777
Set<PosixFilePermission> fp = PosixFilePermissions.fromString("rwxrwxrwx");
Path temp = Files.createTempFile(path, null, ".log", PosixFilePermissions.asFileAttribute(fp));
System.out.println("Temp file : " + temp);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output
Temp file : /home/tvt/workspace/favtuts/temp/12906368521357416981.log
$ pwd
/home/tvt/workspace/favtuts/temp
$ ls -lsah
total 8,0K
4,0K drwxrwxr-x 2 tvt tvt 4,0K Thg 5 20 22:42 .
4,0K drwxrwxr-x 12 tvt tvt 4,0K Thg 5 20 22:24 ..
0 -rwxrwxr-x 1 tvt tvt 0 Thg 5 20 22:42 12906368521357416981.logOutput – On Unix, the group writes file permission may not work as expected.
$ ls -lsah
total 8.0K
4.0K drwxr-xr-x 2 favtuts favtuts 4.0K Jul 20 17:22 .
4.0K drwxr-xr-x 42 favtuts favtuts 4.0K Jul 20 16:06 ..
0 -rwxr-xr-x 1 favtuts favtuts 0 Jul 20 17:22 14080228452578314588.logTo fix it, create the temporary file first, and assign the file permission to the temporary file later.
Path path = Paths.get("/home/tvt/workspace/favtuts/temp/");
Path tempFile = Files.createTempFile(path, null, ".log");
Files.setPosixFilePermissions(tempFile, PosixFilePermissions.fromString("rwxrwxrwx"));Output
$ ls -lsah
total 8.0K
4.0K drwxrwxrwx 2 favtuts favtuts 4.0K Jul 20 17:29 .
4.0K drwxr-xr-x 42 favtuts favtuts 4.0K Jul 20 16:06 ..
0 -rwxrwxrwx 1 favtuts favtuts 0 Jul 20 17:29 11536504893440966062.log4. Create Temporary Files + Java Legacy IO
This example uses the legacy Java IO java.io.* to create a temporary file, it still works perfectly, but the new Java NIO should always be the first choice.
TempFileCreate4.java
package com.favtuts.io.temp;
import java.io.File;
import java.io.IOException;
public class TempFileCreate4 {
public static void main(String[] args) {
try {
File file = File.createTempFile("abc_", ".binary");
System.out.println(file);
} catch (IOException e) {
e.printStackTrace();
}
}
}
Output
/tmp/abc_13872583112153333504.binaryDownload Source Code
$ git clone https://github.com/favtuts/java-core-tutorials-examples
$ cd java-io/temp