What is a safe way to create a Temp file in Java?

Question

I'm looking for a safe way to create a temp file in Java. By safe, I mean the following:

• Name should be unique, even under potential race conditions (e.g. another Thread calls the same func at the same time, or another process runs this code simultaneously)
• File should be private, even under potential race conditions (e.g. another user tries to chmod file at high rate)
• I can tell it to delete the file, without me having to do a generic delete, and risk deleting the wrong file
• Ideally, should ensure file is deleted, even if exception is thrown before I get the chance to
• File should default to a sane location (e.g. the JVM specified tmp dir, defaulting to the system temp dir)

Answer 1

Use File.createTempFile().

File tempFile = File.createTempFile("prefix-", "-suffix");
//File tempFile = File.createTempFile("MyAppName-", ".tmp");
tempFile.deleteOnExit();

Will create a file in the temp dir, like:

prefix-6340763779352094442-suffix

Answer 2

Since Java 7 there is the new file API "NIO2" which contains new methods for creating temnp files and directories. See

• createTempDirectory
• createTempDirectory
• createTempFile
• createTempFile

e.g.

Path tempDir = Files.createTempDirectory("tempfiles");

or

Path tempFile = Files.createTempFile("tempfiles", ".tmp");