java test 2

loop body

A block of statements Executed repeatedly

empty body

A body with no statements Caused by misplaced semicolons

string

A class for working with fixed-string data Unchanging data composed of multiple characters StringBuilder and StringBuffer Classes for storing and manipulating changeable data composed of multiple characters

infinite loop

A loop that never ends Can result from a mistake in the while loop Do not write intentionally

literal string

A sequence of characters enclosed within double quotation marks is a _______.

event-controlled loop

Altered by user input Controlled by the user Executed any number of times

the OR operator

An action to occur when at least one of two conditions is true Written as || Sometimes called pipes

switch statement

An alternative to a series of nested if statements Test a single variable against a series of exact integer, character, or string values

the logical AND operator

An alternative to some nested if statements Used between two Boolean expressions to determine whether both are true Written as two ampersands ( && ) Include a complete Boolean expression on each side Both Boolean expressions that surround the operator must be true before the action in the statement can occur

do... while loop

As a pretest loop: Checks the value of the loop control variable before loop body As a posttest loop Checks the value of the loop control variable At the bottom of the loop After one repetition has occurred Performs a task at least one time You are never required to use this type of loop Use curly braces to block the statement Even with a single statement

Boolean value

Boolean values true and false values Used in every computer decision

compareTo() method

Compares two Strings and returns: Zero: If two Strings refer to the same value Negative number: If the calling object is "less than" the argument Positive number: If the calling object is "more than" the argument if (aWord.compareTo(anotherWord) < 0)

character class

Contains standard methods for testing the values of characters Methods that begin with "is" Such as isUpperCase() Return a Boolean value that can be used in comparison statements Methods that begin with "to" Such as toUpperCase() Return a character that has been converted to the stated form

indexOf() method

Determines whether a specific character occurs within a String Returns the position of the character The first position of a String is zero The return value is -1 if the character does not exist in the String

endsWith() method and startsWith() method

Each takes a String argument Return true or false if a String object does or does not end or start with the specified argument, respectively

validating data

Ensure a value falls within a specified range Use indefinite loops to validate input data If a user enters incorrect data, the loop repeats

equals() method

Evaluates the contents of two String objects to determine if they are equivalent Returns true if objects have identical contents public boolean equals(String s)

while loop

Executes a body of statements continually As long as the Boolean expression that controls entry into the loop continues to be true Consists of: The keyword while Followed by a Boolean expression within parentheses Followed by the body of the loop; can be a single statement or a block of statements surrounded by curly braces

short circuit evaluation

Expressions on each side of the logical operator are evaluated only as far as necessary Determine whether an expression is true or false

substring()method

Extracts part of a String Takes two integer arguments Start position End position The length of the extracted substring is the difference between the second integer and the first integer

case

Followed by one of the possible values for the test expression and a colon

break statements in the switch structure

If a break statement is omitted: The program finds a match for the test variable All statements within the switch statement execute from that point forward

A Boolean expression is evaluated as true or false

If the value of testExpression is true: The entire conditional expression takes on the value of the expression following the question mark If the value is false: The entire expression takes on the value of falseResult An advantage of using the conditional operator is the conciseness of the statement

equalsIgnoreCase() Method

Ignores case when determining if two Strings are equivalent Useful when users type responses to prompts in programs

Unconventional for loops

Initialization of more than one variable Place commas between separate statements Performance of more than one test using AND or OR operators Decrementing or performance of some other task Altering more than one value You can leave one or more portions of a for loop empty

priming read

Input retrieved before the loop is entered Within a loop, the last statement retrieves the next input value and checks the value before the next entrance of the loop

character

Instances hold a single character value Defines methods that can manipulate or inspect single-character data

decision making

Involves choosing among alternative courses of action Based on some value within a program All computer decisions are yes-or-no decisions

if/else

It is most efficient to ask a question most likely to be true first Avoids asking multiple questions Makes a sequence of decisions more efficient

concatenation

Join a simple variable to a String String aString = "My age is " + myAge; Use the + operator

case statement

No need to write code for each case Evaluate char variables Ignore whether it is uppercase or lowercase

toString()method

Not part of the String class Converts any object to a String Converts primitive data types to Strings String theString; int someInt = 4; theString = Integer.toString(someInt);

sequence structure

One step follows another unconditionally Cannot branch away or skip a step

default

Optionally is used prior to any action that should occur if the test variable does not match any case

break

Optionally terminates a switch statement at the end of each case

single-alternative if

Perform an action, or not Based on one alternative

if-else statement

Performs one action when a Boolean expression evaluates as true Performs a different action when a Boolean expression evaluates as false A statement that executes when if is true or false and ends with a semicolon Vertically align the keyword if with the keyword else Illegal to code else without if Depending on the evaluation of the Boolean expression following if, only one resulting action takes place

charAt() method

Requires an integer argument Indicates the position of the character that the method returns Example: myName.charAt(4) outputs "y" if myName=Stacy

conditional operator

Requires three expressions separated with a question mark and a colon testExpression ? trueResult : falseResult; smallerNum=(a < b)? a : b;

length() method

Returns the length of a String

switch

Starts the structure Followed by a test expression enclosed in parentheses

flowchart

Steps in diagram form A series of shapes connected by arrows Programmers use a variety of shapes for different tasks Rectangle to represent any unconditional step Diamond to represent any decision

prefix++

The result is calculated and stored Then the variable is use

if statement

The simplest statement to make a decision A Boolean expression appears within parentheses No space between the keyword if and the opening parenthesis Execution always continues to the next independent statement Use a double equal sign ( == ) to determine equivalency

postfix++

The variable is used Then the result is calculated and stored

regionMatches() method

Two variants that can be used to test if two String regions are equal A substring of the specified String object is compared to a substring of the other If the substrings contain the same character sequence, then the expression is true Otherwise, the expression is false A second version uses an additional boolean argument Determines whether case is ignored when comparing characters

Pseudocode

Use paper and a pencil Plan a program's logic by writing plain English statements Accomplish important steps in a given task Use everyday language

for loop

Used when a definite number of loop iterations is required One convenient statement indicates: The starting value for the loop control variable The test condition that controls loop entry The expression that alters the loop control variable

NOT operator

Written as an exclamation point ( ! ) Negates the result of any Boolean expression When preceded by the NOT operator, any expression evaluated as: true becomes false false becomes true

string

a ___ is a string each crated ___ is a class object it is a variable name not a simple data type

for

a concise format in which to execute loops

string variable

a named object of the string class

range check

a series of if statements that determine whether a value falls within a specified range Java programmers commonly place each else of a subsequent if on the same line

loop

a structure that allows repeated execution of a block of statements

reference

a variable that holds a memory address

incrementing

adding

==

compare 2 strings using the___ operator Not comparing values Comparing computer memory locations Compare contents of memory locations more frequently than memory locations themselves

class string

defined in java.lang.string automatically imported into every program

Use the for loop that contains no body (do-nothing loop) for(x = 0; x < 100000; ++x);

how do you pause a program ?

immutable

objects that cannot be changed, such as a string

iteration

one execution of any loop

indefinite loop

programmer cannot predict number of iterations

definite loop

programmer knows exact number of iterations

accumulating

repeatedly increasing a value by some amount

replace() method

replaces all occurrences of some characters within a string

length()method

returns the numerical length of the string

null string

se the null Java keyword Strings are set to null by default Cannot be used in String methods

decrementing

subtracting

nested if statement

tatements in which an if structure is contained inside another if structure Two conditions must be met before some action is taken Pay careful attention to the placement of else clauses else statements are always associated with if on a "first in-last out" basis

while loop

the loop controlling boolean expression is the 1st statement

do.. while loop

the loop-controlling boolean expression is the last statement

dual alternative if

two possible courses of action

They are convenient when several alternative courses of action depend on a single integer, character, or string value Use only when there is a reasonable number of specific matching values to be tested

why use switch statements