State Chart Diagram :
The statechart diagram models the different states that a class can be in and how that class transitions from state to state. It can be argued that every class has a state, but that every class shouldn’t have a statechart diagram. Only classes with “interesting” states — that is, classes with three or more potential states during system activity — should be modeled.
As per the below diagram, the notation set of the statechart diagram has five basic elements:
the initial starting point, which is drawn using a solid circle; a transition between states, which is drawn using a line with an open arrowhead; a state, which is drawn using a rectangle with rounded corners; a decision point, which is drawn as an open circle; and one or more termination points, which are drawn using a circle with a solid circle inside it. To draw a statechart diagram, begin with a starting point and a transition line pointing to the initial state of the class. Draw the states themselves anywhere on the diagram, and then simply connect them using the state transition lines.
The example statechart diagram above shows some of the potential information they can communicate. For instance, you can tell that loan processing begins in the Loan Application state. When the pre-approval process is done, depending on the outcome, you move to either the Loan Pre-approved state or the Loan Rejected state. This decision, which is made during the transition process, is shown with a decision point — the empty circle in the transition line. By looking at the example, a person can tell that a loan cannot go from the Loan Pre-Approved state to the Loan in Maintenance state without going through the Loan Closing state. Also, by looking at our example diagram, a person can tell that all loans will end in either the Loan Rejected state or the Loan in Maintenance state.
Activity Diagram :
Activity diagrams show the procedural flow of control between two or more class objects while processing an activity. Activity diagrams can be used to model higher-level business process at the business unit level, or to model low-level internal class actions. In my experience, activity diagrams are best used to model higher-level processes, such as how the company is currently doing business, or how it would like to do business. This is because activity diagrams are “less technical” in appearance, compared to sequence diagrams, and business-minded people tend to understand them more quickly.
An activity diagram’s notation set is similar to that used in a statechart diagram. Like a statechart diagram, the activity diagram starts with a solid circle connected to the initial activity. The activity is modeled by drawing a
rectangle with rounded edges, enclosing the activity’s name. Activities can be connected to other activities through transition lines, or to decision points that connect to different activities guarded by conditions of the decision point. Activities that terminate the modeled process are connected to a termination point (just as in a statechart diagram).
Optionally, the activities can be grouped into swimlanes, which are used to indicate the object that actually performs the activity, as shown in below diagram.
In our example activity diagram, we have two swim lanes because we have two objects that control separate activities: a band manager and a reporting tool. The process starts with the band manager electing to view
the sales report for one of his bands. The reporting tool then retrieves and displays all the bands that person manages and asks him to choose one. After the band manager selects a band, the reporting tool retrieves the sales information and displays the sales report. The activity diagram shows that displaying the report is the last step in the process.