Data Types / Variables / Instance + Static

Key Takeaways

Hello guys. Uh so today I'm going to start with the Java next lecture uh which is related to the instance variables and uh the data type. So I have prepared uh this document. In this document you can see uh I have been divided uh there are two subdivisions which is what are the variables and uh where we are going to use those variables and uh apart from this uh the v in the variables types of variables and one of the examples in the realtime scenarios and then uh what are the Java data types and uh after uh discussing with the Java data types uh we by checking with the two different types which is the primitive and the non-prerimitive. Uh how we are going to differentiate between those and some details on those and some examples of those variables and then we are going to convert Java variables their declaration and initiation steps uh with the real-time Java program and try to check with one of the basic example of variables and their uses and the printing of those variables. then uh we'll ask uh some quick questions. Uh we you will be posting the results in your chat sections and then we'll summarize today's lecture. So this is a brief introduction about uh today's lecture. So uh let's uh start the topic uh which uh related to the what is the variable uh so let start with the topic is variables in Java. So uh there are few points what when and how. So uh for any topic or you can say you can also include why as well. So for any topic you need to have remember you have uh these kind of a question that need you need to have in your mind such that what is this when we are going to use this and how we are going to use this and why we are doing so. So these when you cover these four questions in any topic then you are good to go for the next topic and that means you are completely able to understand the topic. So same thing we will be doing with this topic wise. So first is what is variable? So what is variable? Uh it it is a storing thing you can say with the help of variable we can store any sort of data and that and that data can be anything. For example, my name is Ajadya. So AJ is a I wanted to store somewhere else. Similarly, my age is 30. So I wanted to store in some variable that will store that 30 value. Similarly uh my address for example I living in Hana. So this is the place uh where I wanted to store. Similarly I'm uh educator at gigs for gigs. Apart from that I'm also working as a lead engineer as well. So uh these are the different different things that I wanted to convert the data and store into some data some things. So that thing is known as variable. So what is the variable? Variable is a storing thing that can hold some data is known as a variable. As the name suggest when we are going to use the same. So uh whenever we want to have the data and we can reuse those data again and again for reusability of data and that reusability can be anything. For example uh printing for using somewhere else. So that's why when we are going to use these kind of a variables and how we are going to use this so there is a syntax in Java that was followed by so first is we need to provide the data type of the variable then variable name and what data it stored. with a semicolon. So this is the syntax of the variable when we are declaring the types. So it's a uh right now we are understanding these things. So why we are doing so? So same logic y is same is what and when we combine. So that simply means whenever we want to store some data we create a variable with that specific name and whatever the value it can hold we are defining that data type of that variable. So uh let's take one example to understand one of the flow. So let's say int is a data type. We will discussing what is data type later on. Let's say uh if I wanted to store the data in integer 30 is age is a integer value. So I wanted to store 30 in some variable. So int and the variable name. So variable name is age and I want to store value as 30. Similarly aj is my name. So AJ is a string type. So let's create a var data type as string. Name the variable as name and you can assign a value. So this is how we are defining uh the values associated with it and this is the syntax that is associated with the variable in Java. Same thing I have been initiated here. So uh variables are the containers for storing any data values. Each variable in Java must be declared with a data type. The syntax of that is data type. their associated variable name and the value that it can hold. For example, int age is equal to 25, string name is equal to a. This is the example so which you can understand this value. So there are types of variables that you can see in your real times. So first is local variable. Second is instance variable. Third is static variable. And what is the what are the difference between all those three values? So the local variables are defined inside a function and the instance variable are defined on class level but not bounded with class. We will cover this point uh when we you going to understand with the example and the static variable are defined on the class level and bound with the class. So let's take an example to understand each of the variables and then you will understand the difference between instance variable and the static variable. So it's a very important thing that you need to know about it and most of the times in automation perspective you are going to create the variables either on the instance level either on the static level. So these are the basic necessity that you need to know about it. So that's why we will covering uh the point with the example for before that uh let me just uh show you the document we have for that. So uh the type of variables in the Java is basically three types. uh first is local variable so it declares inside the methods. Second is instance variable belongs to the object that simply means it defined on the class level but it associate with the object only static variable belongs to the class and defined in the class level. So let's uh take an example uh with the intelligj. So I was preferred uh you to use the intelligj as a id for any other than uh whether it's you are using eclipse or any sort of values. So uh let's uh this is the maven project I have created. Uh I hope you have uh able to add your lo uh java in your laptop. If you haven't uh just go through one of the video on the YouTube you will find a lot of videos which uh help you to download the Java Java and the IntelligJ in your laptop and try to do so and uh create the Maven project against the same. So uh let's uh create a package class itself. Let's say our lecture is two. So let's make it as two. So inside this lecture we can create a main method. So main method is basically the starting point of the program. For anything uh we need to declare every values here. So let's go one by one and uh declare the associated things. So first is a local variable. So these are the function which is defined on the functional level. So let's uh create one function public void sum int a int b. So this is the variable int c is a local variable because it's inside this function. If you are calling the C value in any other sort of thing, it is not working. So or when any object through which you can call it is not possible because this variable will only lies inside this function. So I'm just printing the value C is equal to A + B. So I'm just uh printing the value whatever I have got through the inside. So basically I if I call the value with sum and provide two values whether it's 10 or 20 it will provide the value of that local variable and add the value simply means 10 + 20 that means it result 30 as a output whenever I call some function with provided two variables inside that part. So this is the local variables are defined inside a function. Now moving on to the instance variable. So these variables are defined on the class level but not bounded with the class. That's what I'm trying to say. So let's say I have created a variable ro number. So this is the variable I have defined on the class level but it is not a static method. So if I want to call the value of that role number we need to use uh in create a reference variable or you can say object or a variable of that class. So let's say I have create a OBJ is equal to new by using OBJ dot ro number I am able to access this function and assign the value whatever I want to if I don't assign a value let's say I have assigned value as 30 and print the value let's say I have printing the value Now this one so it will print you instead of 30 let's uh print 20. So it will print 20. So on every object I can change the value. But if I create a new reference variable let's say I have created a object one and I didn't provide any value. So by it is bounded with the it is not bounded with the class. So that means it is by default holding whatever the value. Let's say integer is by default holds a zero value. So it will return us the zero value. So if I make the variable at static that simply means it is bound with the class not with the class or you can say bound with object. So whenever I make a changes here the updated value which is 20 is also reflected here. So this is the main difference between static and non-static. So that's why for making a complete value throughout the cycle execution when we started the automation or whenever the web driver we needs to provide with the all classes we are going to define the variable as static instead of non-static. So if I make a static that simply means it will default the value again to the variable. So let's uh call the value let's say 10 20 see uh this is the value I have. So by default it start from executing like this. It will create a reference variable with with this. So I have assigned the value as 20 as as a object level one. So that simply means this row number is being changed from zero value to 20 then it will print 20. Then I have created a new variable and without assigning any new value with that variable that simply means it is uh on that specific variable this role number will act as a zero value and print a zero. Similarly in this it will print 30 as a output. So this is the execution of the program. Let's uh try to run the value and check the result. See 20 and then zero and then sum is 30. So before moving on to that let me uh share with diagram so that can help you. So this is OBJ1. This is OBJ2. So inside that role number is going to be assigned. By default it is zero. By default it is zero. This is the role number and this is the role number. So if I make the changes in object J on that value instead of zero make it as 20 that if I print the value ro now 20 displays 20 but I haven't make the changes in object level two with the role number so that's why it is printing as zero to us so this is the main difference between static and a non-static if I make the value as static that simply means means it will not bound with the value of the CL object. So it it is bound with the class. So let's say this is the class and inside that class the role number will persist. So if using OBJ1 I make a changes in role number in from zero to 20 that simply means it is now holding value 20. If I again calling the OBJ role number that simply means it will print value 20. So this is the main difference between static and the non-static and in the real time we are declaring most of the variables as static because we want that to hold till the complete execution of your automation script. So if I make it as static I have make the static variables. Now change see the difference before that it is printing 20 sum is 30 and similar like this. So let me uh store the value to show you the difference between the value. This is the old data without providing the static variable. So we are using the instance variable. So let's uh make execute the same and check what it changed the value. See now we have instead of zero value it is printing the 20 value because we have make the changes as 0 to 20 like this and the updated value to will associate with the class not with the object that simply means we are calling this variables only. So this is the main difference between a static variable and a instance variable. So this is the example. This is the uh I have shown one one of the flow and we have seen with the Java flow as well. Uh I hope everyone I hope uh this is the uh you have any concern you can drop a note into the chat section I will able to uh get your point. Uh so we can proceed with the next point. So this is the complete information about the variables. So let's move on to the data type. Hello, hello Escapail. And uh yeah. So let's move on to the Java types. So the Java data types has categorized into two subdivisions with the it is primitive and second is non-primitive. So primitive are those data type which are by default provided by the Java. So there are eight types of primitive data types that was provided by the Java. So this is the diagram that you need to know. But being a automation tester you don't need to remember the bit size because that doesn't bother you much because our main focus is to automate. So we just need to have idea what sort of value that a v variables can hold. See without data type we cannot create a variable. So we first need to understand what is Java data types. So there are these are the eight primitive data types that has been provided by the Java which is byte, short, integer, long, float, double, car and boolean. So these are the primitive data types. So you don't need to remember all of the values. Majorly you are going to use the integer value for uh storing the int value whether it's 100 minus 0 and uh minus 10 whatever the value you want to have hold long uh if the value is beyond the 32,000 the value of the s so then that's why we are going to use the long vari long integer. So there is a different definition that uh in the end l value is going to be shown that it is a part of a long variable. Float uh simply means uh the decimal value for example 2.3 4.5 anything sort of values can be held using a float. Similarly for larger value in the float we can use double value. So uh int long float and double these are the basic necessity that you need to know. Then you need to understand the character. So character can hold a single value. So let's say my name is AJ. So this this is a string. So how many character is this? There are there are four character inside it. What are those characters? First character is A. Second character is J. Second third character is A and the last character is Y. So there are four characters inside which combination of this is known as string. So combination of characters will result to a string. So care it can hold like this. You can see car g I is a variable name I have created and a is a character that can hold. Similarly uh boolean is the value which can hold either true value or a false value. So most of the times boolean is being used for verifications. You have for any testing sort of thing we need to know that expected result and the actual result uh you know need to verify. If both are true that simply means it is a boolean value. If both is not matching that simply means it will result as false. So that's why we are going to use in automations assert class that will have a two functions assert true or assert false. If the actual result and the expected result doesn't meet up that simply means boolean is being used which returns a value as false. If the both are the matching that simply means boolean is a value that it can hold and it can hold true value. So this is the main thing that you need to know about these primitive data type. So uh and the non-primitive data types are those data types which are not part of a primitive you can say which are uh kind of a classes interfaces which has been provided by the Java like string is a class arrays is a classes you can see I have created one class like this and we have declared a data type which is this and we are calling a or we are creating a instance variable with obj. Similarly uh classes has been changed to the interfaces as well. So uh same thing is been associated with it like this. So let's uh create one example to show you the value. So string is a uh you can say primitive data type or sorry non-primitive data type. Let's say obj. So if I print the value of this obj value is see if I print the value it will print the value a j see so this string can hold a non-primitive data type so this is the b difference between non-primitive and the primitive data type. So when we uh move to the declaration and initiation of a Java variables or a Java data type, there are three things that you need to know. First is declaration, second is initiation and third is combination of those values. So declaration simply means without providing any value we are defining the value like we have done in this previous example. We have defined this without holding any value. This is known as declaration. We have declared the variable but haven't used or haven't assigned any value. Here we are assigning the value. So this is known as initiation. For most of the time when you are doing the automation you are declaring the variables here and initiation of those variables will be done on the later functions or you can say in the separate functions. So this is the major point that you need to know but not every time you need to create with that you can declare the values and initiate the value combined with this example. Let's say take an example as a primitive data type. Let's say this is the primitive data type I have defined. So I have declared a variable with a which of data type as integer which is of primitive and it is holding a value of 30. So initiation and declaration both combined in a single value. This is a primitive type. Similarly, non-primitive let's say name is also a combined non primitive type. So we can also use those variables and print the value whatever I whatever we want. So let's uh print the value. So let's say age is name. So by using system.out.print ln I can print the value in the console. So this is the main thing that you need to know about the Java. See it is printing the value with the name. So let me just add a space for more differentiation thing. See age is 30 and name is AJ. So this is how we can declare and initiate the Java data type and the variable. See declaration initiation combine with this example. This is the basic thing that you need to know about it. I hope everyone able to uh understand the topic. you can just uh chat uh drop a node if you are able to understand the point in the live chat as well. So uh let's uh do a quick uh understanding and you can say quick revision what are the basic thing that you need to know. So uh by default you can this is the example of a string. We can have a multiple non- primitive example as well. Let's say add. So by using this we can declare a array and we can print the value whatever inside this. So this is also an example of combination of non-primitive and a primitive data type. So this is the brief introduction about the variable and their Java data types. So we have covered what are the variables. These are the basic containers. This is the example which syntax you need to know about it. uh there are three different types whether it's a local instance and static. Most of the time in any automation project you are going to use these two things which is a instance variable and the static variables. And then we have seen with one of the examples of the printing all those specific values. This is the example which is the instance variable. This is the static variable. This is the local variable. We have assigned the value uh the instance variable using setting of those values and this is the local variable we have done. Then we have move to the Java data types. Uh using that Java Java data type we have categorized into two different types. First is the primitive type uh where we have defined with all eight different types and then we have moved to the non-primitive type which is classes, arrays, interface and classes. Uh string. So uh string is example we have seen arrays have we have seen classes we have seen. So these are the different types we have seen and then we move to the Java variable and the declaration initiation steps. So the content here we have uh done with the declaration like this initiation with x is equal to 10 and we can combine the declaration initiation on primitive and non-prerimitive as well. So uh these are the few examples which integer a is equal to 5 float pi is equal to 3.14 character is equal to a. So these are the different uh through which we can combine the value of initiation and declaration. This is one of the examples where we have added uh integer age is equal to 20 name as RIA marks whatever 85.5% boolean value is pass is true and then we are printing all those values with those variables we have been created above whether it's a name whether it's a age whether it's a marks whether it's a past so uh these are the few questionire that uh you can provide provide answer in the chat sections. I will wait uh till 30 second and you can uh drop or not. So these first question is basically what are the default value of a string variable and which data type is used to store the true and false. So uh drop point on these two point uh let's start with the first question. What are the default value of a string variable? Yeah, we got the answer as a by default value of is this string value as null. If we don't provide any value on those string let's say I haven't provided the value like this and if I print the value what is the output of that see because uh it is not initiated any value so that is assigned the value as null. That simply means it is throwing a null pointer exception. You can see this is the main difference between a non- primitive and a primitive data type. If I don't provide any value for example a let's say age is a and I don't provide any value of that integer it simply means we haven't initiate the value it's say I have just printing the value of a that simply means we haven't initiate the value variable might not have been initiated as well so by default it is holding a zero value and which data type is used to store the true and false. So the true and false value can be hold by the boolean value. So boolean is also a a primitive data type that can hold value as a name uh true or a false. Let's say assert check. Okay. So by default uh this assert this variable as boolean data type can hold value either true or a false. Let's say I can provide the value as true and I print the value of variable. So it will print the value as true because it can hold the value as true. See if I make the changes as false that means the system.out.print ln will print value of that variable as false. Let me uh make run the same. See it is holding the true and false value. So this is the basic point that you need to know for any assertion. We are going to use this boolean lot of time. because it is helping you if I in uh add the dependencies with the associated with that assertion class there are predefined functions which is known as assert true or assert false if I provide the value as a true that simply provide uh doesn't throw any assertion error if we are providing the boolean value as false that it will throw us a false value in that part. So this is the main difference between the point we have discussed so far. So the summary the end. So this is the complete lecture between uh variables and the different types of things in Java. So let's uh summarize the topic and then we can uh wrap it up uh the today's lecture. So the summary uh that simply here simply means var summary here is variable that can hold the data value is known as variables must be declared with the data types and we have understand there are two different data types first is primitive and non-primitive. We can define the variables with either of those. Then Java has eight primitive types which we have uh covered this bite, short, integer, long, float, then double, then character and then boolean. You need to understand how we are initiation and declaration with this. And most of the times in automation perspective we are generally do declaration and then initiation are being done on the function level or you can say actionable method level as well. Then at the end non-prerimitive types are based on the objects which when uh whatever the object we have created for example string the arrays one the classes we have seen. So that's all uh for today's lecture guys uh I hope everyone able to understand the point. So uh try in the real time try to install the Java in your own laptop use the intelligent and try to create some uh variables on their own. try to create all the primitive data types and print the value on their own and then try to check the creation of the object on the class and similarly using uh string as well then you are good to go with the next following lectures that we are going to start our today's topic then thank you everyone that's all for today's you can uh wrap it