Returns the application's {@code SecurityManager} instance accessible in the backing map using the
{@link #getSecurityManagerName() securityManagerName} property as the lookup key.
<p/>
This implementation guarantees that a non-null instance is always returned, as this is expected for
Environment API end-users. If subclasses have the need to perform the map lookup without this guarantee
(for example, during initialization when the instance may not have been added to the map yet), the
{@link #lookupSecurityManager()} method is provided as an alternative.
@return the application's {@code SecurityManager} instance accessible in the backing map using the
{@link #getSecurityManagerName() securityManagerName} property as the lookup key.
Returns the application's {@code SecurityManager} instance accessible in the backing map using the {@link #getSecurityManagerName() securityManagerName} property as the lookup key. <p/> This implementation guarantees that a non-null instance is always returned, as this is expected for Environment API end-users. If subclasses have the need to perform the map lookup without this guarantee (for example, during initialization when the instance may not have been added to the map yet), the {@link #lookupSecurityManager()} method is provided as an alternative.
@return the application's {@code SecurityManager} instance accessible in the backing map using the {@link #getSecurityManagerName() securityManagerName} property as the lookup key.