System.setProperty is not working for applets. Because JVM already running before applet start. In this case we use applet parameters like this:
deployJava.runApplet({
id: 'MyApplet',
code: 'com.mkysoft.myapplet.SomeClass',
archive: 'com.mkysoft.myapplet.jar'
}, {
java_version: "1.6*", // Target version
cache_option: "no",
cache_archive: "",
codebase_lookup: true,
java_arguments: "-Djava.net.preferIPv4Stack=true"
},
"1.6" // Minimum version
);
You can find deployJava.js at https://www.java.com/js/deployJava.js