Section 1
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Escape sequence
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Last updated
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Date created
Mar 1, 2020
Cards (66)
Section 1
(50 cards)
Escape sequence
Begins with a backslash followed by a character
Represents a single nonprinting character
char aNewLine = '
';
showInputDialog() method
Six overloaded versions Returns a String representing a user's response
Reasons for using named constants:
Make programs easier to read and understand Enable you to change a value at one location within a program Reduce typographical errors Stand out as separate from variables
Variable
A named memory location Used to store a value Can hold only one value at a time Its value can change
boolean variable
Can hold only one of two values true or false boolean isItPayday = false;
Dialog boxes used to accept user input
Input dialog box Confirm dialog box
Keyboard buffer
Location in memory that stores all keystrokes, including Enter To avoid issues, add an extra nextLine()method call to retrieve the abandoned Enter key character after numeric or next() inputs
Reference types
More complex data types
Data type
A type of data that can be stored How much memory an item occupies What types of operations can be performed on data
Concatenated
A numeric variable is concatenated to a String using the plus sign The entire expression becomes a String The println() method can accept a number or String
Assignment operator
The equal sign (=) The value to the right is assigned to the variable on the left
Literal constant
Value taken literally at each use
Scanner object
Breaks input into units called tokens
Declaring and Using Constants and Variables
System.in object
Standard input device Normally the keyboard Access using the Scanner class
There is a problem when using one numeric
Scanner class retrieval method or next()method before using the nextLine()method
String
A built-in class Stores and manipulates character strings String constants are written between double quotation marks
Variable declaration
A statement that reserves a named memory location Includes: Data type Identifier Optional assignment operator and assigned value Ending semicolon
Variations of the integer type
byte short long
Primitive type
A simple data type
A named constant:
Should not change during program execution Has a data type, name, and value Has a data type preceded by the keyword final Can be assigned a value only once Conventionally is given identifiers using all uppercase letters
Numeric constant
As opposed to a literal constant
Prompt
A message requesting user input
Declaring Variables
Declare multiple variables of the same type in separate statements on different lines int myAge = 25; int yourAge = 19; When declaring variables of different types, you must use a separate statement for each type
Assignment
An assignment made after a variable is declared
Operand
A value used on either side of an operator
Standard arithmetic operators
Perform calculations with values in programs
char data type
Holds any single character
后面size in bytes背下来！！
Name variables
Use naming rules for legal class identifiers
Floating-point data types
float double
int data type
Stores an integer, or whole number Value from -2,147,483,648 to +2,147,483,647
Initialization
An assignment made when declaring a variable
Unnamed constant
No identifier is associated with it
Scope
The area in which a data item is visible to a program, and in which you can refer to it using its simple identifier. A variable or constant is in scope from the point it is declared. Until the end of the block of code where the declaration lies
Input dialog box
Asks a question Provides a text field in which the user can enter a response
Boolean logic
Based on true-or-false comparisons
Associativity
The order in which operands are used with operators
Floating-point number
Contains decimal positions
print() or println() statement
Use alone or in combination with a String
Place constant character values within single quotation marks
char myMiddleInitial = 'M';
Relational operator (comparison operator)
Compares two items
Significant digits
Refers to mathematical accuracy
To produce console output on multiple lines in the command window, use one of these options:
Use the newline escape sequence Use the println() method multiple times
Constant
Cannot be changed while program is running
Section 2
(16 cards)