What is the default encoding of the JVM?

The default character set of the JVM is that of the system it's running on. There's no specific value for this and you shouldn't generally depend on the default encoding being any particular value.

It can be accessed at runtime via Charset.defaultCharset(), if that's any use to you, though really you should make a point of always specifying encoding explicitly when you can do so.

Note that you can change the default encoding of the JVM using the confusingly-named property file.encoding.

If your application is particularly sensitive to encodings (perhaps through usage of APIs implying default encodings), then you should explicitly set this on JVM startup to a consistent (known) value.

To get default java settings just use :

java -XshowSettings 

You can use this to print out the JVM defaults

import java.nio.charset.Charset;
import java.io.InputStreamReader;
import java.io.FileInputStream;

public class PrintCharSets {
        public static void main(String[] args) throws Exception {
                System.out.println("file.encoding=" + System.getProperty("file.encoding"));
                System.out.println("Charset.defaultCharset=" + Charset.defaultCharset());
                System.out.println("InputStreamReader.getEncoding=" + new InputStreamReader(new FileInputStream("./PrintCharSets.java")).getEncoding());
        }
}

Compile and Run

javac PrintCharSets.java && java PrintCharSets

It's going to be locale-dependent. Different locale, different default encoding.