Lecture 1.pdf

Language Fundamentals +++++++++++++++++++++ 1. Identifiers A name in java program is called "identifier" The name can be a classname,interfacename,enumname,varaiblename,methodname and label name. class Test{ public static void main(String[] args){ int x = 10; }...

Language Fundamentals +++++++++++++++++++++ 1. Identifiers A name in java program is called "identifier" The name can be a classname,interfacename,enumname,varaiblename,methodname and label name. class Test{ public static void main(String[] args){ int x = 10; } } Identifiers: Test,main,String,args,x ++++++++++++++++++++++ Rules for Identifiers +++++++++++++++++++++ Rule1: The allowed characters in java identifiers are a to z, A to Z,0 to 9,_,$ Rule2: If we use any other character, then the program would result in "CompileTime Error". Rule3: Identifiers should not start with digits eg: PWSKILLS123---> valid 123PWSKILLS---> invalid Rule4: java identifiers are case sensitive,as such Java language only is case sensitive(JVM) class Test{ int number = 10; int NUMBER = 100; int NuMbeR = 1000; } Rule5: There is no constraint of the length of the java identifiers,but it is not recomended to take the length more than 15. eg: int physicsWallahAlakhPandeyJavaWithMicroservices = 100; Rule6: Reserve words or builtin words can't be used as "java identifiers". if we try to use then it would result in "CompiletimeError". int,if,float,else,while,for,do,..... => reserve words/built in words/keywords Inbuilt classname,interfacename,enumname can be used as a "identifier". Eventhough classname,interfacename,enumname can be used as an identifier, we don't recomend. eg:: class Test{ public static void main(String[] args){ int int=10; //CE int if =10; //CE int while=100;//CE } } class Test{ public static void main(String[] args){ int String =10;  } } ++++++++++++++++++++++++++++++++++++++++++++++++ Identify which are valid and invalid identifiers ++++++++++++++++++++++++++++++++++++++++++++++++ 1. _$_ ===> valid 2. ca$h ==> valid 3.java2share=> valid 4. all@hands=> invalid 5.123abc => invalid 6.Total# => invalid 7.Int => valid(not recomended) 8.Integer=> valid(not recomended) 9.int => invalid(reserve word) 10.tot123=> valid