By Mr. Muhammad Pervez Akhtar

 The general environment  The first program  Comments, Main, Terminal Output  Primitive types  Primitive types, Constants, Declaration and Initialization, Terminal Input and Output  Basics Operators  Assignment Operators, Binary Arithmetic Operators, Unary Operators, Type Conversion Operators

 Conditional Statements  Relational and equality operators, Logical operators, The if statement, The while statement, The for statement, The do statement, break and continue, The switch statement, The conditional operator  Methods  Overloading of method names  Storage classes

 Java Source code resides in files whose names end with the.java suffix  The local compiler, javac, compiles the program and generates.class files, which contain bytecode  Java bytecodes represent the portable intermediate language that is interpreted by running the Java interpreter, java.  The interpreter is also known as the Virtual Machine  Java programs, input can come from one of many places:  Standard input, Command Line Arguments, A File, GUI Component

 Save program as FirstProgram.java  Compile program as javac FirstProgram.java  Run program as javac FirstProgram  Four things to note in program  Comments, class, main method, standard output

 Comments are non-compiled and non- executable code  Three types of comments  // : single line comment, inherited from C  /*…*/: multi line comments inherited from c  /**…*/: information for javadoc utility to generate documentation form comments  Why Comments are needed?  Make code easier for humans to read  Helps programmers to modify the program  Commented program is a good sign of programmer

 Java program consists of interacting classes which contain methods and data elements  Methods can be invoked using object of its class  Static method can be invoked without object of its class  Public static void main(String args[]) is special method with void return type, command line argument, public access modifier and is static  It is the method that executes first of all

 System.out.println: is the primary output mechanism in java  Also called standard output (output on console)  System.out.print: is another way of output  println vs print  println shifts control to start of next line after output  but print does not shifts control to next line  Can output integer, floating point, string, or some other type

 Integer constants can be represented in either decimal, octal, or hexadecimal notation  Octal notation is indicated by a leading 0; hexadecimal is indicated by a leading 0x or 0X  Equivalent ways of representing the integer 37: 37,045,0x25 ::Decimal, Octal and Hexa  Character constant is enclosed with a pair of single quotation marks, as in 'a‘  Internally, this character sequence is interpreted as a small number  String constant consists of a sequence of characters enclosed within double quotation marks, as in "Hello"

 Escape sequence is a constant but with special meanings  It starts with a ‘\’ backslash followed by a character to print  Followings are commonly used:  ‘\n’New line character  ‘\\’Backslash character  ‘\’’Single quotation mark  ‘\”’Double quotation mark

 A primitive type, is declared by providing its type, its name, and optionally its initial value  Type should be primitive type (int, float etc)  The name must be an identifier, that consists of:  Any combination of letters, digits, and the under- score character but it not start with a digit  Reserved words are not allowed  Not reuse identifier names that are already visibly used  Are case sensitive, age or Age are different

 Basic formatted terminal I/O is accomplished by nextLine and println  The standard input stream is System.in  The standard output stream is System.out  Formatted I/O uses the String type  + combines two Strings  If one of the argument is not a String, a temporary String is created for it if it is a primitive type  For input, we associate a Scanner object with System.in.  Scanner has different methods for different primitive types

 Operators are symbols to perform an operation  Operators are used to form expressions  Expression is combination of variables, constants and operators  Following are the types of operators  Assignment Operators =, +=, -=, *=, /=  Binary Arithmetic Operators +, -, *, /, %  Unary Operators ++, --, - ::prefix or postfix use  Type Conversion Operators Generate a temporary entity of a new type

 Statements that affect the flow of control  Relational and Equality operators , >=, ==, !=  Logical Operators  AND, OR, NOT or conjunction, disjunction and negation respectively  &&, ||, ! Is another representation  ! Has highest precedence and && has higher precedence than ||  && and || called short-circuit operators

 The IF, IF THAN ELSE statement  Two common mistakes  Loops the While, For, and Do statements

 Break and Continue statements  Break statement terminate execution in the middle of a repeated statements (loop)  Continue Statement Give up on the current iteration of a loop and go on to the next iteration

 Switch Statement  Suitable when multiple branches against one Condition  The conditional operator  a shorthand for simple if-else statements  testExpr ? yesExpr : noExpr

 Known as a function or procedure :: main()  A method header consists of a name, a (possibly empty) list of parameters, and a return type  The actual code to implement the method, sometimes called the method body  A method declaration consists of a header plus the body  Overloading of method  Several methods may have the same name and be declared in the same class scope as long as their signatures(that is, their parameter list types) differ.

 Local Variables:  Entities that are declared inside the body of a method are local variables  Can be accessed by name only within the method body  Global Variables  A variable declared outside the body of a method is global to the class  if the word static is used, is similar to global variables in other languages  Static Final Variable  If both static and final are used, they are global symbolic constants