Week 5 and 6 Flashcards
The order of statement execution in a method is called the …
“flow of control”
- Sequence - sequential
- selection – statements that allow us to decide whether or not to execute a particular statement. (if, if-else, switch statements)
- iteration – repetition – statements that allow us to execute a statement (while, do-while, for statements.)
- Boolean expressions are used by Selection and Iteration statements to determine whether a statement is executed.
Logical operators – Boolean operands
True or False results
- ! Logical NOT (applied before && and ||)
- && Logical AND (applied ||) (SHORT circuited if the first is false other isn’t evaluated.
- || Logical OR (SHORT circuited if the first is TRUE then the other isn’t evaluated.
If-else statement
An if statement uses a boolean expression as
its condition.
While loop
A while statement (or while loop) will continually execute a statement or block of statements as long as its condition (Boolean expression) is true; i.e., it repeats the statement or block) until the condition is false.
-ANY variables in the Boolean expression need to be initialized BEFORE the loop.
The ArrayList class defines …
an object that can hold a list of other objects called elements.
Common Methods of an ArrayList
-add(): adds an object to the list
-remove(): removes an object or the object at a specified index
-get(): returns the object at the specified index
-indexOf(): returns the index of the specified object
(indexed from 0)
-size(): returns the number of objects in the list
When comparing type char…
using the equality and relational operators (==, !=, , <=, >=)
When comparing types double and float…
should use == or != with care due to possible rounding; best to check that the absolute value of the difference between two items is less a specified tolerance
Object types (other than the numeric wrapper classes) can be compared using …
the equality operators (==, !=), but in most cases the object’s equals() or compareTo() method should be used
values of char types A-Z vs a-z
A-Z numeric values 65-90. a-z numeric values 97-122
some classes provide a compareTo() which returns…
an int rather than a Boolean
equalsIgnoreCase and compareToIgnoreCase
methods for the String class
nested statements
when an if-else is inside another if-else statement. same with while statements.
infinite loops
common logical error
break statement
in a loop will skip the rest of the code in that iteration and exit the loop
continue statement
will skip the rest of the code in that iteration and attempt the next iteration of the loop
when reading a file use a …
FileNotFoundException (throw)
iterator
an iterator is an object that allows you to process a collection of items one at a time.
- hasNext() that returns true if there is at least one more item to process
- next() returns the next item
Switch statement:
- the switch statement – very similar to the “if” statement (input is a char)
- A switch statement can jump directly to the correct case, whereas an if-else-if-else as to evaluate each boolean expression until one is true or all are false
- see diagrams
Ternary operator
a way to make if-else statement more concise. (condition ? if result : else result)
Do-While loop
Similar to a while loop, except that the Boolean expression is evaluated at the nd of the loop (the do-while statement is a post-test loop whereas the while statement is a pre-test loop)
§ This means the body of the do-while will always be executed at least once, regardless of whether the boolean expression is true
-see diagrams
For loop
Similar to the while loop, but well-suited for iterating a specific number of times or over a range of values. (for (initialization; termination – Boolean; increment))
An ArrayList is an Iterable object
which means it can be the target of the “for-each” statement
-for (“ArrayList Object type” “variable use to reference current item in each iteration”: variable name for the ArrayList)
