Java Nuts and Bolts

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Java Nuts and Bolts

• Variables and Data Types
• Operators
• Expressions
• Control Flow Statements
• Arrays and Strings

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public class BasicsDemo public
static void main(String args)
int sum 0 for (int current
1 current lt 10 current)
sum current
System.out.println("Sum " sum)

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Variables and Data Types

• Variables contain data that can change during
  program executiontype name
• All Variables have type, name, scope
• Two Major Categories (Type)
• Primitive
• Reference
• Purity Format and Size

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// integers byte
largestByte Byte.MAX_VALUE
short largestShort Short.MAX_VALUE
int largestInteger Integer.MAX_VALUE
long largestLong
Long.MAX_VALUE // real
numbers float largestFloat
Float.MAX_VALUE double
largestDouble Double.MAX_VALUE
// other primitive types
char aChar 'S' boolean
aBoolean true
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Variable Type

• Determines Values Variable can have
• Determines Operations that can be performed on a
  variable
• Primitive Single value of appropriate size and
  format
• Reference to value or set of values that variable
  represents (classes, interfaces, arrays)

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Primitive Data Types
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Variable Names

• Program refers to variable value by name
• Composed of Unicode Characters
• Must not use keywords or boolean literals (true
  or false)
• Unique within scope
• Convention begin with lowercase
• More than one word, capitalize

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Scope

• Block of code where variable is accessible
• Determined by location in program
• Four Categories
• Member Variable
• Local Variable
• Method Parameter
• Exception-Handler Parameter

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• Member Variable is a member of a class or object
  which canbe declared anywhere in a class, but
  not in a method.
• Local Variables are declared anywhere in a
  method.
• Method Parameters are used to pass values to
  methods (arguments)
• Exception-handler Parameters are arguments to
  exceptionhandling methods.

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Variable Initialization

• Local and member variables can be initialized
  when declared.
• final keyword value cannot change after
  initialization.
• Variables must be initialized before use
• Good Programming Practice to do it at declaration

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Operators

• Perform a function
• Unary, binary, tertiary,
• Unary Prefix or Postfix (i, i)
• Binary Infix (a b)
• Returns a value
• Arithmetic, Bitwise and Logical, Assignment

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Expressions

• The Workers
• Application of an operator is an expression
• An expression is a series of variables,
  operators, and method calls (constructed
  according to the syntax of the language) that
  evaluates to a single value.
• Precedence

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Control Flow

• while
• if-then-else
• switch
• for loops
• continue

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Arrays and Strings

• Array Declaration Array is an class, so an
  array object must be instantiated (new)
• Instantiation allocates memory to the object
• Arrays can contain any valid Java data type
• String objects, not character arrays
• Concantenation operator ()

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