JavaChapter_2 – Flashcards
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The ____ method is similar to the println method, except that it does not advance to the next line
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print
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Therefore anything printed after a print statement will appear on the?
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same line
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operator (+) is used to append one string to the end of another
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string concatenation
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It can also be used to append a number to a string A string literal cannot be broken across two lines in a program
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String Concatenation
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operator is also used for arithmetic addition
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+
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+++ If both operands are strings, or if one is a string and one is a number, it performs
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string concatenation
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+ operator If both operands are numeric?
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it adds them
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The + operator is evaluated left to right, but _____can be used to force the order
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parentheses
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is a series of characters that represents a special character
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escape sequence
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sequence begins with a backslash character ()
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escape
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is a name for a location in memory that holds a value
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variable
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specifies the variable's name and the type of information that it will hold
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variable declaration
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changes the value of a variable
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assignment statement
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is an identifier that is similar to a variable except that it holds the same value during its entire existence
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constant
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As the name implies, it is constant, not?
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variable
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The compiler will issue an ____if you try to change the value of a constant
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error
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In Java, we use the___ modifier to declare a constant
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final
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First, they give meaning to otherwise unclear literal values Example: MAX_LOAD means more than the literal 250 Second, they facilitate program maintenance If a constant is used in multiple places, its value need only be set in one place Third, they formally establish that a value should not change, avoiding inadvertent errors by other programmers
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Constants
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There are eight primitive data types in Java
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Four of them represent integers: byte, short, int, long Two of them represent floating point numbers: float, double One of them represents characters: char And one of them represents boolean values: boolean
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The difference between the numeric primitive types is their ?
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size and the values they can store:
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A ____variable stores a single character
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char
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Note the difference between a primitive character variable, which holds only one character, and a ____ object, which can hold multiple characters
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String
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is an ordered list of characters, with each character corresponding to a unique number
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character set
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variable in Java can store any character from the Unicode character set
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char
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set uses sixteen bits per character, allowing for 65,536 unique characters
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Unicode character
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It is an international character set, containing symbols and characters from many world languages
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Unicode character
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character set is older and smaller than Unicode, but is still quite popular
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ASCII character set
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are a subset of the Unicode character set, including:
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ASCII characters
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value represents a true or false condition
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boolean
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true and false are the only valid values for a boolean type
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reserved words
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variable can also be used to represent any two states, such as a light bulb being on or off
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boolean
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is a combination of one or more operators and operands
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expression
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compute numeric results and make use of the arithmetic operators:
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Arithmetic expressions
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If either or both operands are floating point values, then the result is a
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floating point value
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If both operands to the division operator (/) are integers, the result is an
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integer (the fractional part is discarded)
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returns the remainder after dividing the first operand by the second
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The remainder operator (%)
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Operators
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can be combined into larger expressions result = total + count / max - offset
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precedence
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Operators have a well-defined _____ which determines the order in which they are evaluated
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Multiplication, division, and remainder
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_____, _____, and_____ are evaluated before addition, subtraction, and string concatenation
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parentheses
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Arithmetic operators with the same precedence are evaluated from left to right, but can be ____used to force the evaluation order
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expression tree
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The evaluation of a particular expression can be shown using an ____ ____
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assignment operator
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has a lower precedence than the arithmetic operators
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The increment (++) and decrement (--)
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operators use only one operand
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The statement count++ is functionally equivalent to
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count = count + 1
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postfix or prefix
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The increment and decrement operators can be applied in ____form: count++ or ____ form: ++count
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The entire right-hand expression is evaluated first, then the result is combined with the original variable •Therefore result /= (total-MIN) % num
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result = result / ((total-MIN) % num) is equivalent to?
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If the operands to the += operator are strings, the assignment operator performs ______ _____
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string concatenation
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The behavior of an assignment operator (+=) is always consistent with the behavior of the corresponding operator ;
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(+)
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Widening conversions
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are safest because they tend to go from a small data type to a larger one (such as a short to an int);
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Narrowing conversions
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can lose information because they tend to go from a large data type to a smaller one (such as an int to a short);
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In Java, data conversions can occur in three ways
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assignment conversion, promotion,casting;
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Promotion
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happens automatically when operators in expressions convert their operands;
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Casting
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is the most powerful, and dangerous, technique for conversion
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widening and narrowing conversions
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can be accomplished by explicitly casting a value
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cast
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To ______, the type is put in parentheses in front of the value being converted;
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input
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Programs generally need _____on which to operate
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Scanner class
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provides convenient methods for reading input values of various types
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Scanner object
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can be set up to read input from various sources, including the user typing values on the keyboard
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System.in object
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Keyboard input is represented by the?
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Scanner scan = new Scanner(System.in)
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The following line creates a Scanner object that reads from the keyboard
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new operator
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creates the Scanner object
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Scanner object
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can be used to invoke various input methods, such as: answer = scan.nextLine()
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java.util class
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The Scanner class is part of the ______ library, and must be imported into a program to be used
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nextLine method
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reads all of the input until the end of the line is found
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white space
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is used to separate the elements (called tokens) of the input
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White space
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includes space characters, tabs, new line characters
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string
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The next method of the Scanner class reads the next input token and returns it as a ______
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Methods
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such as nextInt and nextDouble read data of particular types
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picture or drawing
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must be digitized for storage on a computer
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A picture
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is made up of pixels (picture elements), and each pixel is stored separately
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picture resolution
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The number of pixels used to represent a picture is called the ?
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monitor resolution
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The number of pixels that can be displayed by a monitor is called the
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pixel
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Each _____ can be identified using a two-dimensional coordinate system
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coordinate system
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When referring to a pixel in a Java program, we use a _____with the origin in the top-left corner Y X (0, 0) (112, 40) 112 40
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Red, Green, and Blue
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Every color can be represented as a mixture of the three additive primary colors?
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RGB value
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Each color is represented by three numbers between 0 and 255 that collectively are called an ?
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color
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in a Java program is represented as an object created from the Color class
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A Java application
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is a stand-alone program with a main method (like the ones we've seen so far)
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A Java applet
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is a program that is intended to be transported over the Web and executed using a web browser
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An applet also
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can be executed using the appletviewer tool of the Java SDK
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main method
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An applet doesn't have a_____?
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paint method
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is executed automatically whenever the applet's contents are drawn
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paint method
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accepts a parameter that is an object of the Graphics class
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Graphics object
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defines a graphics context on which we can draw shapes and text
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Graphics class
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has several methods for drawing shapes
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An applet
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is embedded into an HTML file using a tag that references the bytecode file of the applet
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The bytecode
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version of the program is transported across the web and executed by a Java interpreter that is part of the browser
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A shape
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can be filled or unfilled, depending on which method is invoke
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The method parameters
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specify coordinates and sizes
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Shapes with curves
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, like an oval, are usually drawn by specifying the shape's bounding rectangle
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An arc
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can be thought of as a section of an oval
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An arc
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is defined by an oval, a start angle, and an arc angle:
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Every drawing surface
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has a background color
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Every graphics context
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has a current foreground color
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