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Default Value

c:\temp\ /tmp/

The default value will differ based upon the operating system that java is running on.

java.io.tmpdir Explained

The java.io.tmpdir system property defines the file system path of a temporary directory for use by the java runtime.

As of Java 20, a warning message will be displayed if the temporary directory does not exist upon startup of the JVM:

WARNING: java.io.tmpdir directory does not exist

Related System Properties

Here are some other File Path related Java system properties:

• file.encoding
• file.separator
• jdk.io.File.enableADS

Supported Since

Java has supported the java.io.tmpdir system property since at least Java 1.4, support may go back even further.

Setting java.io.tmpdir on Startup

You can set the java.io.tmpdir java system property during startup of the java runtime using the -D command line argument:

java -Djava.io.tmpdir=c:\temp MyAppMain

You may also be able to specify java.io.tmpdir via the JAVA_TOOL_OPTIONS environment variable:

JAVA_TOOL_OPTIONS=-Djava.io.tmpdir=c:\temp

Setting / Reading java.io.tmpdir at Runtime

You can set java.io.tmpdir at runtime with the following Java code:

System.setProperty("java.io.tmpdir", "c:\temp");

WARNING: Depending on the property and JVM version using setProperty may or may not work if the JDK Java class that uses this variable has already been loaded. The value of the java.io.tmpdir system property may be cached within an internal private static variable of the implementing class.

To read the value of java.io.tmpdir at runtime, you can use this Java code:

String propertyValue = System.getProperty("java.io.tmpdir");
if (propertyValue != null) {
    System.out.println("java.io.tmpdir = " + propertyValue);
} else {
    System.out.println("java.io.tmpdir was null");
}

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