Now considered a Sun legacy product, PersonalJava is or was a software development platform for creating network-capable applications for various consumer devices for office, home, and mobile use. Taking Java's Write Once, Run Anywhere approach to a new level, PersonalJava can be used to create applications for televisions, set-top boxes, medical equipment, and telephones (among a great number of other possibilities), in addition to desktop computers. The platform consists of the Java Virtual Machine and an optimized class library. Java code is said to be well suited to these applications because it is portable, reliable, and Internet-ready. Java code can also be downloaded at runtime so that applications can be upgraded or extended. The Virtual Machine ensures a secure execution environment .
PersonalJava has been replaced by a Connected, Limited Device Configuration (CLDC) profile in Sun's Java 2 Platform, Micro Edition (J2ME), a newer platform for mobile or micro-device application development.