The installer examines the computer on which you are installing and identifies the Java ES components that are already installed. The installer then checks at several levels to make sure that all existing components are at the appropriate release level to interoperate successfully. The installer informs you about those software components that are incompatible and must be upgraded or removed.
Similarly, the installer checks for Java ES shared components (see Shared Components), such as J2SE or NSS, that are already installed. If the installer finds versions of shared components that are incompatible, it lists them. If you proceed with installation, the installer automatically upgrades the shared components to newer versions.