A data type in a programming language is a set of data with values having predefined characteristics.data The language usually specifies:  the range of values for a given data type,  how the values are processed by the computer  and how they are stored.

Primitive Data Types: There are eight primitive data types supported by Java. Primitive data types are predefined by the language and named by a keyword. Let us now look into detail about the eight primitive data types. byte:  Byte data type is an 8-bit signed two's complement integer.  Minimum value is -128 (-2^7) and maximum value is 127 (inclusive)(2^7 -1)  Default value is 0  Byte data type is used to save space in large arrays, mainly in place of integers, since a byte is four times smaller than an int.  Example: byte a = 100, byte b = -50 short:  Short data type is a 16-bit signed two's complement integer.  Minimum value is -32,768 (-2^15) and maximum value is 32,767 (inclusive) (2^15 -1)  Short data type can also be used to save memory as byte data type. A short is 2 times smaller than an int  Default value is 0.  Example: short s = 10000, short r = int:  Int data type is a 32-bit signed two's complement integer.  Minimum value is - 2,147,483,648.(-2^31) and maximum value is 2,147,483,647(inclusive).(2^31 -1)  Int is generally used as the default data type for integral values unless there is a concern about memory.  The default value is 0.  Example: int a = , int b =

long:  Long data type is a 64-bit signed two's complement integer.  Minimum value is -9,223,372,036,854,775,808.(-2^63)  Maximum value is 9,223,372,036,854,775,807 (inclusive). (2^63 -1)  This type is used when a wider range than int is needed.  Default value is 0L.  Example: long a = L, int b = L float:  Float data type is a single-precision 32-bit IEEE 754 floating point.  Float is mainly used to save memory in large arrays of floating point numbers.  Default value is 0.0f.  Example: float f1 = 234.5f

double:  double data type is a double-precision 64-bit IEEE 754 floating point.  This data type is generally used as the default data type for decimal values, generally the default choice.  Default value is 0.0d.  Example: double d1 = boolean:  boolean data type represents one bit of information.  There are only two possible values: true and false.  This data type is used for simple flags that track true/false conditions.  Default value is false.  Example: boolean one = true char:  char data type is a single 16-bit Unicode character.  Minimum value is '\u0000' (or 0).  Maximum value is '\uffff' (or 65,535 inclusive).  Char data type is used to store any character.  Example: char letterA ='A'

 Changing a value from one data type to another type is known as data type conversion.  Conversion methods change the type of input objects.  Data type conversions are either widening or narrowing, it depends on the data capacities of the data types involved.  There are different ways of changing an entity of one data type into another data type.

EX: integer (4 Byte) converted into double (8 Byte) Widening conversion is allowed in the following cases:  byte can be converted to short, int, long, float, or double  Short can be converted to int, long, float, or double  char can be converted to int, long, float, or double  int can be converted to long, float, or double  long can be converted to float or double  float can be converted to double

int a = 100; double b = a; System.out.println(b);

Narrowing conversion is allowed in these cases:  short can be converted to byte or char  char can be converted to byte or short  Int can be converted to byte, short, or char  long can be converted to byte, short, or char  float can be converted to byte, short, char, int, or long  double can be converted to byte, short, char, int, long, or float

 Narrowing conversion should follow the following thumb rule  Information loss  The narrowing conversion must be explicit.  The target type need to be specified in parentheses. Listing 1: Representing the narrowing conversion public class MainClass { public static void main(String[] args) { long a = 10; int b = (int) a; // narrowing conversion System.out.println(a); System.out.println(b); }

 To convert a string into an int, use: String str = "1234"; int num = Integer.parseInt(str); // returns primitive data type String str = “1234”; Int num = Integer.valueOf(str); // returns JAVA instance  To convert a number into a string, use: int num = 1234; String str = Integer.toString(num); int num = 1234; String str = String.valueOf(num);

 format() formats almost any number of values based on a format string, with many options for precise formatting  The format method formats multiple arguments based on a format string.  The format string consists of static text embedded with format specifiers; except for the format specifiers, the format string is output unchanged.  % is a special character denoting that a formatting instruction follows.  [.precession] denotes the precision of floating point numbers in the output. That is basically the number of decimal digits you wish to print on the output. But it can be used for other types to truncate the output width  type along with %, are the only mandatory formatting arguments. type simply denotes the type of the object that will be formatted in the output. For integers that is d, for strings that is s, for floating point numbers that is f, for integers with hex format that is x. EX. %.2f

public class Root2 { public static void main(String[] args) { int i = 2; double r = Math.sqrt(i); System.out.format("The square root of %d is %f.%n", i, r); } The output:  The square root of 2 is  d formats an integer value as a decimal value.  f formats a floating point value as a decimal value.  n outputs a platform-specific line terminator.