Java is a programming language for Internet and intranet applications from the javasoft division of Sun. Java was modeled after C++. Java supports two types of application development, one is developing Standalone Applications and Other is developing Internet based Applets. Applets are the applications which run on internet or intranet and are called from browser.

Unlike all other platforms, Java never creates a executable file (.exe). Exe file is generally dependent on platform, so if we want to implement an exe file for Windows or Unix or any other platform, we will have to recompile the executable with some modifications. In case of Java, the source code of Java (Generally .java file) is compiled to give "byte code", which can not run on its own. The byte code is interpreted and converted to machine code at run time. This code conversion is done by Java virtual machine (JVM). So any browser or platform which has JVM inbuilt can execute Java programs. So Java programs become independent of hardware platform or browser or operating system.

Now Java has launched a new version called Java 2 which has advanced features. We will discuss those features and also talk about writing advanced applications like Multi tiered applications with Java in following articles.

Version 1.2 of the Java Development Kit (JDK) adds the following major features to the Java platform and JDK tools since 1.1.

• Access Control introduces the concepts of "permission" and "policy." When code is loaded, it is assigned "permissions" based on the security policy currently in effect. Each permission specifies a permitted access to a particular resource (such as "read" and "write" access to a specified file or directory, "connect" access to a given host and port, etc.). The policy, specifying which permissions are available for code from various signers/locations, can be initialized from an external configurable policy file. Unless a permission is explicitly granted to code, it cannot access the resource that is guarded by that permission.
  These new concepts of permission and policy enable the Java Development Kit to offer fine-grain, highly configurable, flexible, and extensible access control. Such access control can now not only be specified for applets, but also for all code written in the Java programming language, including applications, and beans.

  • Certificate interfaces enable developers to build tools for parsing certificates, enforcing their own site-specific certificate policies, and managing local databases of certificates.

  • X.509 v3 implementation of the new, supported certificate interfaces.

  • The keytool, jar, jarsigner, and policytool security tools - keytool creates key pairs and self-signed X.509 v1 certificates, and manages keystores. Keys and certificates are used to digitally sign your applications and applets. A keystore is a protected database that holds keys and certificates. jarsigner signs JAR (Java Archive Format) files, and verifies the signature(s) of signed JAR files. It accesses the keystore when it needs to find the key when signing a JAR file. keytool and jarsigner replace javakey. policytool creates and modifies the external policy configuration files that define your installation's security policy.