Data Types Variables And Arrays
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Use of Command line Arguments class Cmdline { public static void main(String args[]) { int count,i=0; String s1; count=args.length; System.out.println(“No.of Arg=“+count); while(i
Chapter -3
Data types variables and Arrays
By:A.J.Patankar
Data Types Data Types
Primitive
Non-Primitive
Classes Numeric
Arrays
Non Numeric Interface
int
char float
boolean
Variables A variable is a named memory location that can hold a value. type varName Format to declare variable. Type
Desc.
Keyword
Character
16 bit
char
Boolean
True/false
boolean
Byte
8 bit
byte
Short
16 bit
short
Integer
32 bit
Int
Long
64 bit
long
Float
32 bit
float
Double
64 bit
double
Types of Variables 1. Primitive Variables: A value of primitive type holds value of that exact primitive type. 2. Reference Variable: A variable of reference type can hold a null reference A reference to any object whose class is assignment compatible with type of variable.
Kinds of Variables Class variable Instance variable Array Components Method Parameters Constructor Parameters Exception Handler Parameters Local Variables
Scope & Lifetime of Variables Java allows variables to be declared within any block. A block defines a scope of variable There are 2 types of Scope 1:Class Scope & 2: Method Scope A variable declared inside the scope is not visible outside the scope Variable declared inside becomes localized and protect it from unauthorized access and modifications Two variables one in inner scope and one in outer scope cannot have same value
Example #1 class ScopeDemo { public static void main(String args[]) { int a=2; if(a==2) { int b=4; System.out.println(“a=“+a+”b=“+b); } b=10; //An error System.out.println(“a=“+a); } }
Example #2 class TypePromotion { public static void main(String args[]) { int i; float f; i=10; f=23.25f; System.out.println(i*f); } }
One Dimensional Arrays One Dimensional array is a list of variable of the same type that are accessed through a common name. An individual variable in the array is called an array element. Format : type varName[ ]= new type[size];
Ex: One Dimensional Arrays class ArrayDemo { public static void main(String args[]) { int myarray[]={33,71,-16,45}; System.out.println(“myarray.length=“+myarray.length); System.out.println(myarray[0]); System.out.println(myarray[1]); System.out.println(myarray[2]); System.out.println(myarray[3]); } }
Multidimensional Arrays It is arrays of arrays To declare multidimensional array variable specify each additional index using another set of square brackets. example: int numbers[ ][ ]=new int[3][5] ;
Multidimensional Arrays class TwoDArray { public static void main(String args[]) { int marray [ ][ ] =new int[3][2]; marray[0][0]=33; marray[0][1]=71; marray[1][0]=-16; marray[1][1]=45; marray[2][0]=99; marray[2][1]=27; System. out.println(“marray.length=“+marray.length); System.out.println(marray[0][0]); System.out.println(marray[0][0]); System.out.println(marray[0][0]); System.out.println(marray[0][0]); System.out.println(marray[0][0]); System.out.println(marray[0][0]); } }
Type Conversion In java it is possible to assign value of one type to variable of another type Example: int i=260; byte b=(byte) i; double d= 1071.89; byte db= (byte) d;
Chapter -3
Data types variables and Arrays
By:A.J.Patankar
Data Types Data Types
Primitive
Non-Primitive
Classes Numeric
Arrays
Non Numeric Interface
int
char float
boolean
Variables A variable is a named memory location that can hold a value. type varName Format to declare variable. Type
Desc.
Keyword
Character
16 bit
char
Boolean
True/false
boolean
Byte
8 bit
byte
Short
16 bit
short
Integer
32 bit
Int
Long
64 bit
long
Float
32 bit
float
Double
64 bit
double
Types of Variables 1. Primitive Variables: A value of primitive type holds value of that exact primitive type. 2. Reference Variable: A variable of reference type can hold a null reference A reference to any object whose class is assignment compatible with type of variable.
Kinds of Variables Class variable Instance variable Array Components Method Parameters Constructor Parameters Exception Handler Parameters Local Variables
Scope & Lifetime of Variables Java allows variables to be declared within any block. A block defines a scope of variable There are 2 types of Scope 1:Class Scope & 2: Method Scope A variable declared inside the scope is not visible outside the scope Variable declared inside becomes localized and protect it from unauthorized access and modifications Two variables one in inner scope and one in outer scope cannot have same value
Example #1 class ScopeDemo { public static void main(String args[]) { int a=2; if(a==2) { int b=4; System.out.println(“a=“+a+”b=“+b); } b=10; //An error System.out.println(“a=“+a); } }
Example #2 class TypePromotion { public static void main(String args[]) { int i; float f; i=10; f=23.25f; System.out.println(i*f); } }
One Dimensional Arrays One Dimensional array is a list of variable of the same type that are accessed through a common name. An individual variable in the array is called an array element. Format : type varName[ ]= new type[size];
Ex: One Dimensional Arrays class ArrayDemo { public static void main(String args[]) { int myarray[]={33,71,-16,45}; System.out.println(“myarray.length=“+myarray.length); System.out.println(myarray[0]); System.out.println(myarray[1]); System.out.println(myarray[2]); System.out.println(myarray[3]); } }
Multidimensional Arrays It is arrays of arrays To declare multidimensional array variable specify each additional index using another set of square brackets. example: int numbers[ ][ ]=new int[3][5] ;
Multidimensional Arrays class TwoDArray { public static void main(String args[]) { int marray [ ][ ] =new int[3][2]; marray[0][0]=33; marray[0][1]=71; marray[1][0]=-16; marray[1][1]=45; marray[2][0]=99; marray[2][1]=27; System. out.println(“marray.length=“+marray.length); System.out.println(marray[0][0]); System.out.println(marray[0][0]); System.out.println(marray[0][0]); System.out.println(marray[0][0]); System.out.println(marray[0][0]); System.out.println(marray[0][0]); } }
Type Conversion In java it is possible to assign value of one type to variable of another type Example: int i=260; byte b=(byte) i; double d= 1071.89; byte db= (byte) d;
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