Structured Programming Summary

• Java includes only single-entry/single-exit control statements—there is only one way to enter and only one way to exit each control statement.
• Connecting control statements in sequence to form structured programs is simple. The final state of one control statement is connected to the initial state of the next—that is, the control statements are placed one after another in a program in sequence. We call this control-statement stacking.
• The rules for forming structured programs also allow for control statements to be nested.

• Structured programming promotes simplicity.
• Bohm and Jacopini: Only three forms of control are needed to implement an algorithm:
  • Sequence
  • Selection
  • Repetition
• The sequence structure is trivial. Simply list the statements to execute in the order in which they should execute.
• Selection is implemented in one of three ways:
  • if statement (single selection)
  • if…else statement (double selection)
  • switch statement (multiple selection)
• The simple if statement is sufficient to provide any form of selection—everything that can be done with the if…else statement and the switch statement can be implemented by combining if statements.
• Repetition is implemented in one of three ways:
  • while statement
  • do…while statement
  • for statement
• The while statement is sufficient to provide any form of repetition. Everything that can be done with do…while and for can be done with the while statement.

• Combining these results illustrates that any form of control ever needed in a Java program can be expressed in terms of
  • sequence
  • if statement (selection)
  • while statement (repetition)

  and that these can be combined in only two ways—stacking and nesting