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Lecture2_Datatypes_Variables.ppt
- 1. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Core Java Programming Data-types and Variables
- 2. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR •JVM • JVM (Java Virtual Machine) is a software. It is a specification that provides runtime environment in which java byte code can be executed. It is not physically exists. • JVMs are not same for all hardware and software, for example for window os JVM is different and for Linux JVM is different. JVM, JRE and JDK are platform dependent because configuration of each OS differs. But, Java is platform independent.
- 3. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR •JRE • JRE is an acronym for Java Runtime Environment. It is used to provide runtime environment. It is the implementation of JVM.
- 4. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR •JDK • The Java Development Kit (JDK) is the primary componens. It physically exists. It is collection of programming tools and JRE, JVM.
- 5. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Keywords in Java... • There are 49 reserved keywords currently defined in the Java language. These keywords, combined with the syntax of the operators and separators, form the definition of the Java language. These keywords cannot be used as names for a variable, Class, or method.
- 6. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Data Types in Java... • In Java , there are really two different categories in which data types have been divided : – 1. Primitive Types – 2. Reference Types
- 7. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Data Types in Java... Reser.Word Data Type Size byte Byte length integer 1 byte Short Short Integer 2 bytes int Integer 4 bytes long Long Integers 8 bytes float Single precision number 4 bytes double Double Precision number 8 bytes char Character (16 bit Unicode) 2 bytes boolean Has value true or false A Boolean Value
- 8. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Range of Data Types… Data Type Range byte -128 to 127 short -32768 to 32767 int -2,147,483,648 to 2,147,483,647 long -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807 float 3.4e-038 to 3.4e+038 double 1.7e-308 to 1.7 e+308 char 0 to 65535
- 9. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Identifiers in Java... • Identifiers are the names of variables , methods , classes , packages and interfaces. Identifiers must be composed of letters , numbers , the underscore and the dollar sign.$. • They cannot contain white spaces, Identifiers may only begin with a letter, the underscore or a dollar sign. You cannot begin a variable name with a number. All variable are case sensitive for example • MyVariable is not same as myVariable
- 10. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Invalid Variable Names... • My Variable // contains a space • 9pins // Begins with a digit • a+b // the plus sign is not an alphanumeric character • testing 1-2-3
- 11. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Integer Variables... • The following lines show how to create variables of integer types : • long My_First_Byte = 10; • int a=20;
- 12. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Boolean Variables... • A Boolean Variable is not a number. It can have one of two values true or False. There are two ways to set its values . • The first way to do this is explicitly. • Ex :a) boolean firstboolean = false; • b) boolean firstboolean = secondboolean;
- 13. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Float & Double Variables... • In Java, floating point numbers are represented by the types float and double . Both of these follow a standard floating point specification. • float a = 35.6f; double x = 356556.25; • float b = 35.7F; double y = 356556.25; • a,b,x,y are variables. • Note : 35.6f and 35.7F are single Precision Literals. As Floating point numbers are treated as double precision quantities. To force them to single precision we use f and F.
- 14. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Literals... • Literals are pieces of Java source code that indicates explicit values. Literals in Java refer to fixed values that do not change during the execution of a program. Java supports several types of constants. A) Integer Constants B) Real Constants C) Single Character Constants D) String Constants
- 15. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR String Literals... • The String Literal is always enclosed in double quotes . Java uses a String class to implement Strings whereas C and C++ use an array of characters. • For example : • String poem = “Java supports Multithreading”;
- 16. PRANVEER SINGH INSTITUTE OF TECHNOLOGY, KANPUR Boolean Literals... • Boolean Literal can have either of the values : true or false. • They do not correspond to the numeric value 1 and 0 as in C and C++.