CSAwesome - Unit 2b Loops Vocabulary

Body of a Loop

The single statement or a block of statements that can be repeated (a loop may not execute at all if the condition is false to start with). In Java the body of the loop is either the first statement following a while or for loop is the body of the loop or a block of statements enclosed in { and }.

For Loop

A loop that has a header with 3 optional parts: initialization, condition, and change. It does the initialization one time before the body of the loop executes, executes the body of the loop if the condition is true, and executes the change after the body of the loop executes before checking the condition again.

For Each Loop

Used to loop through all the elements of a collection (like a list or an array) and each time through the loop set a variable to the next item from the collection

Infinite Loop

A loop that never ends.

Loop

A way to repeat one or more statements in a program.

Nested Loop

One loop inside of another.

Out of Bounds error

A run-time error that occurs when you try to access past the end of a string or list in a loop.

Trace Code

Writing down the values of the variables and how they change each time the body of the loop executes.

While Loop

A loop that repeats while a Boolean expression is true.

while

used to start a while loop

for

used to start a for loop or a for each loop

System.out.println(variable)

used to print the value of the variable. This is useful in tracing the execution of code and when debugging.

Off by one errors

occurs when the iteration statement loops one time too many or one time too few.

Input-controlled loops

often use a sentinel value that is input by the user like “bye” or -1 as the condition for the loop to stop. Input-controlled loops are not on the AP CSA exam, but are very useful to accept data from the user

loop control variable

used in the boolean condition of the loop; a counter that controls how many times to repeat the loop

accumulator pattern

an algorithm that involves storing and updating an accumulator value within a loop, for example to compute a sum or average of a set of values.

int sum = 0;

for (int i = 1; i <= 100; i++) {

sum += i;

}

System.out.println("The sum of 1 through 100 is " + sum);

The sum variable is the accumulator variable, the whole thing is an accumulator pattern.

String Traversals or String Processing algorithms

algorithms where the code steps through a string character by character.

There are standard string algorithms to:

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• Find if one or more substrings has a particular property

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• Determine the number of substrings that meet specific criteria

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• Create a new string with the characters reversed

Nested iteration statements (or nested loops)

are iteration statements that appear in the body of another iteration statement. Or in simpler terms, a loop inside of another loop.

run-time analysis or a statement execution count

indicates the number of times a statement is executed by the program. Statement execution counts are often calculated informally through tracing and analysis of the iterative statements.