Selection/Decision Structures


Another collection of the most fundamental structures has to do with making decisions or branching within a program.

For example, the tax rate depends on income level.  In order to compute taxes appropriately, a programmer needs to use different rates depending on the income levels.  

There are endless examples of such situations. 

The following three diagrams represent the three fundamental selection/decision structures.

The first one is the basic If - Then structure.  Though the syntax is different in Java and doesn't require the then word.  For example, if someone has a grade above a particular level then they should get an A.



The next structure relates to having another option built in if the condition being evaluated is false.  For example either someone passes a class or they fail it.  If their grade is above a certain level, they pass.  Else they fail.  This is an If - Then - Else sort of structure, though the syntax is different in Java.



Finally, we have situations where there is something that has some specific varied outcomes such as several different grade values, income tax brackets or paying for PMI on a mortgage.  These sorts of things result in a large variety of different cases and implemented through a switch structure in Java.