UNIVERSITY AT BUFFALO, THE STATE UNIVERSITY OF NEW YORK
The Department of Computer Science & Engineering

STUART C. SHAPIRO: CSE 115 C

Reading

Brown U. Notes, Chapter 8

Barnes, Chapter 6

If you have set of basic operations/actions/behaviors, how can you combine them to make a more complex operation/action/behavior?

According to a theorem proved by Corrado Böhm and Giuseppe Jacopini (CACM, 1966), all you need is:

1. Sequence: Do one action, and then another, and then another, etc.
2. Selection: Do one action or another, based on some condition.
3. Loop: Repeatedly do an action as long as some condition holds.

Sequence

You have already written methods that consist of a sequence of statements. They are executed in the order they appear in the program.

A block is a sequence of statements surrounded by braces (curly brackets), { ... }.
Anywhere a statement is legal, a block may be used.

Selection (Conditionals)

A conditional statement in Java is
     if (condition) statement1
     [else statement2]
(Remember, either statement could be a block.)

condition is a Java expression that evaluates to a boolean value (true or false).

If the condition evaluates to true, statement1 is executed.
If the condition evaluates to false, statement1 is not executed, and if the else clause is present, statement2 is executed.

A conditional expression in Java is
     (condition ? expression1 : expression2)
The parentheses are optional.

If the condition evaluates to true, the conditional expression evaluates to the value of expression1.
If the condition evaluates to false, the conditional expression evaluates to the value of expression2.

boolean is a Java primitive (base) type like int and double.
It has only two values, true and false.

boolean operators:

not:

p	!p
true	false
false	true

and, or, exclusive or, equivalent, not equivalent:

p	q	p && q	p || q	p ^ q	p == q	p != q
true	true	true	true	false	true	false
true	false	false	true	true	false	true
false	true	false	true	true	false	true
false	false	false	false	false	true	false

Relational operators:
Operate on two numbers, evaluates to a boolean.