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ONE MISTAKE in VIDEO : The term Access specifier is used by c++ programmers not in java. In JAVA Officially we use ACCESS MODIFIER but i have used access spe...

What is variable ? 1. Variable is a name of memory location where data is stored. 2. The value of variable can vary, means value can be changed.

There are three types of variables : 1. Local Variables : 1.1 DECLARED : inside methods, constructors or blocks. 1.2 SCOPE : within the methods, constructors or blocks but not outside of them. 1.3 MEMORY ALLOCATION : when method, constructor or block is invoked variable is allocated; when exits, variable gets destroyed. 1.4 STORED MEMORY : stack memory 1.5 DEFAULT VALUES : doesnt have any default value, so it should be assigned before use. 1.6 ACCESS MODIFIERS : public, private or protected access specifier cannot be used.

2. Instance Variable : 2.1 DECLARED : in a class but outside methods, constructors or blocks. 2.2 SCOPE : inside the class, within all methods, constructors or blocks. 2.3 MEMORY ALLOCATION : when object is created, variable allocated memory; when object destroyed, memory releases. 2.4 STORED MEMORY : heap memory 2.5 DEFAULT VALUES : have default values eg. int has 0 value, boolean false, String null etc. 2.6 ACCESS MODIFIERS : any access modifiers can be used. 2.7 HOW TO ACCESS : a) can be accessed directly by calling the variable name inside the class. b) in static methods they should be called using the fully qualified name, ie objectRefName.variable_name.

3. static variable : 3.1 DECLARED : with static keyword in a class but outside methods, constructors or blocks. 3.2 SCOPE : similar to instance variable ie inside the class, within all methods, constructors or blocks including static part 3.3 MEMORY ALLOCATION : when we run program and .class file is loaded, variable allocated; when class file unload, variable gets destroyed. 3.4 STORED MEMORY : non-heap memory or static memory 3.5 DEFAULT VALUES : have default values eg. int has 0 value, boolean false, String null etc. 3.6 ACCESS MODIFIERS : any access modifiers can be used. 3.7 HOW TO ACCESS : a) directly b) by using class name b) by using object reference name

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The Codeless Code: Case 19

Case 19: By any other name

In this case we see the Scribe Qi being asked why he has named the clans and temples of their monastary, but not the individual monks in his documents. The scribe responds that when writing numbers would you name every number 7. The scribe is rebutted by a note on his door the next day with a static variable declaration of NUM_DAYS_IN_WEEK.

Here we see that it is useful to name significant numbers, rather than use them throughout your application code. Many times a programmer might lazily write 7′s anywhere there’s a expectation of length of a week, or 365 for days of the year(except for leap year of course) and 24 for hours in a day. This is done mostly because these magic numbers are considered to be relatively standard and should not change, so why spend the time to define a Static variable and using it throughout the code, and having to remember this token instead of the simple number 7?

This is because while it may be obvious when you initially write the code, it may be ambiguous to others in some cases, and it is also possible that as the world slows in orbit around the sun we may see more days in a year, and our calendar itself while fairly stable today, may find itself replaced in the future by a yet unnamed calendar specification. What is concrete today may not be the same tomorrow, and being able to simply redefine a static var will certainly be easier than refactoring every usage of the number in code.

So consider defining your special numbers, and make it easier for future developers to handle change.

#static variables #special numbers

Two faces of STATIC

By default all functions are implicitly declared as extern, which means they're visible across translation units. But when we use static it restricts visibility of the function to the translation unit in which it's defined. So we can say Functions that are visible only to other functions in the same file are known as static functions. Let use try out some code about static functions. main.c #include "header.h" int main() { hello(); return 0; } func.c #include "header.h" void int hello() { printf("HELLO WORLD\n"); } header.h view plainprint? #include static int hello(); If we compile above code it fails as shown below view plainprint? $gcc main.c func.c header.h:4: warning: "hello" used but never defined /tmp/ccaHx5Ic.o: In function `main': main.c:(.text+0x12): undefined reference to `hello' collect2: ld returned 1 exit status It fails in Linking since function hello() is declared as static and its definition is accessible only within func.c file but not for main.c file. All the functions within func.c can access hello() function but not by functions outside func.c file. Using this concept we can restrict others from accessing the internal functions which we want to hide from outside world. Now we don't need to create private header files for internal functions. Note: For some reason, static has different meanings in in different contexts. 1. When specified on a function declaration, it makes the function local to the file. 2. When specified with a variable inside a function, it allows the variable to retain its value between calls to the function. See static variables. It seems a little strange that the same keyword has such different meanings...

#static variables #static keyword #static functions #different ways to use static #coding everything