Mid Term Exam #2 Reference

Mid Term #2 Reference

Selections

if (expression) { 
    ... 
}

if (expression) {
    ....
} else {
    ....
}

if (expression) {
    ....
} else if (expression) {
    ....
} else if (expression) {
    ....
} else {
    ....
}

switch (expression) {
    case x:
    case y:
    case z:
    default:
}

Also: break; statement

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Regular Expressions

Classes/Methods:

• String.matches(regex)
• java.util.regex.Pattern
  • Pattern.compile(regex)
  • Pattern.compile(regex, flags)
  • patternObj.matcher(string)
• java.util.regex.Matcher
  • matcherObj.matches()
  • matcherObj.lookingAt()
  • matcherObj.find()
  • matcherObj.reset()
  • matcherObj.reset(string)

Steps to using RegEx classes:

1. Create the Pattern object
2. Create the Matcher object on the Pattern object for a specific String
3. Execute one of the Matcher methods
4. To use it again with a different string, reset the Matcher object

Regular Expression Syntax

Regex Syntax

• Single token from a set []
• Not one of these [^]
• Token range [a-z] [A-Z] [0-9] etc
• Quantifiers: + ? * {n} {n,m} {n,}
• Metacharacters: \d \D \w \W . (dot) \s \S
• OR operator |
• Groups ()
• Escaping characters:
  • must escape . ^ $ * + ? ( ) [ { / |
  • inside character classes you must escape ^ - ] \

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Iteration

Loop Syntax

while (condition) {

}

do {

} while (condition);

for (initializer; condition; increment) {

}

Priming-Read/Continuing-Read Pattern

priming read
while (condition)
    ...
    continuing read

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Mid Term #1 Reference

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Basic Stuff

class header: public class ...
main() header: public static void main(String[] args)

Semi-colons: at the end of executing statements, such as:

• variable/constant declarations/initialization
• assignment statements
• statements that print output to the screen
• calculations
• creating a scanner
• statement that gets user input using a scanner
• import statement

No semi-colon after:

• class header
• main method header
• if/else-if/else block header

IPO: Input / Processing / Output

Import statement:
import package.name.Class;

Escape sequences:

• \n newline
• \u unicode

Categories of Errors:

• Compilation/Syntax
• Execution/Runtime
• Logic

Generate a Random Number:

between 1 and n:
(int)(Math.random() * n + 1)

between x and y:
(int)(Math.random() * (y - x + 1) + x)

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Data Types

Reference types

• String

Primitive Types:

• byte, short, int, long (null value 0)
• float, double (null value 0.0)
• char (null value '\0')
• boolean (null value false)

Notations for floating point values:

• Standard Decimal Notation: 123.456789
• Scientific Notation: 9.823x10²
• Exponential Notation: 7.7777e4

Floating Point Number Storage (IEEE 754)

Data Type	Description	# bits for Coefficient	# bits for Exponent	# bits for Sign
float	Single-precision floating-point	23	8	1
double	Double-Precision floating-point	52	11	1

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Expressions and Math

Variable declaration:
type varname;

Variable declaration with initialization:
type varname = value;

Constants:

• public static final
• outside the main()
• must be initialized upon declaration

Assignment operator: =

Concatenation operator: +

String methods:

• equals()
• equalsIgnoreCase()

Arithmetic operators: + - / * %

Unary Arithmetic operators: ++ -- (both pre-fix and post-fix)

Augmented Assignment operators: += -= /= *= %=

Math Class methods

• pow(), sqrt(), cbrt()
• abs()
• floor(), ceil()
• min(), max()

Casting operator: (type)

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Input and Output

Getting Input

Scanner: java.util

Scanner whatever = new Scanner(System.in);

Scanner methods:

• next(), nextLine()
• nextInt(), nextDouble()
• nextBoolean()
• Get one character: next().toUpperCase().charAt(0) (or can use toLowerCase() instead of toUpperCase())

Displaying Output

System.out methods:

• print(), println()
• printf(), format()

Formatting

Conversion Codes and other Symbols:

• %d, %f, %s
• %c, %b, %e
• - (left justify)

Standard format for format specifier:
%[width].[digits][code]

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Boolean Expressions

Relational/Conditional Operators:

• >, >=
• <, <=
• ==, !=

Logical Operators:

• && AND
• || OR
• ! NOT

Conditional Operator: ?:
(booleanExpression) ? valueIfTrue : valueIfFalse

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