Mid Term Exam #1 Reference

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)

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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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