Past Simple

The past simple tense specifically talks about something that happened in the past and it’s finished.

🔰 We need to consider the verbs carefully when we use the past tense. There are 2 kinds of verbs in English. such as,

1. Regular.
2. Irregular.

👉 Regular:-

Those verbs whose simple past and past participle are formed by adding the suffix “ed”, “d”, or “ied” can be known as regular verbs.

• work → worked
• play → played
• clean → cleaned
• watch → watched

🔰 Making regular Past verbs:

Most verbs: add [ed]

🔸 walk → walked

🔸 cook → cooked

Verbs ending in e: add [d]

🔸 bake → baked

🔸 use→ used

Verbs ending in consonant and y: drop [y] add [ied]

🔸 cry→ cried

🔸 study→ studied

Verbs ending in vowel and y: add [ed]

🔸 play→ played

🔸 enjoy→ enjoyed

Verbs ending with Consonant + vowel + Consonant : [double last letter +ed]

🔸 stop→ stopped

🔸 plan→ planed

👉 Irregular:-

Verbs that either change their forms completely or remain the same can be known as irregular verbs.

• go → went
• see → saw
• buy → bought
• run → ran

Examples:

1. I wanted. ( past verb of want)
2. She wanted.
3. He drank. (past verb of drink — irregular verb)
4. They drank.
5. They watched. (past verb of watch — regular verb)
6. He watched.
7. I went. (past verb of go — irregular verb)
8. It went.
9. They played. (past verb of play — regular verb)
10. She played.

👉 Affirmative Form:-

1. Lisa went to the supermarket yesterday.
2. Sam cooked a tasty dinner yesterday.
3. My brother saw a movie last week.
4. I traveled to France last year.
5. I washed the dishes.
6. My mother bought a dress for me.
7. I learned how to play the guitar five months ago.
8. My brother waited hours at the railway station.
9. I played tennis.
10. People lived in caves a long time ago.

👉Negative Form:-

1. I didn’t play football yesterday.
2. They didn’t go to the theater last month.
3. She didn’t arrive on time this morning.
4. You didn’t go to bed early.
5. The police didn’t find any clues.
6. We didn’t make a cake for you.
7. He didn’t feel sad yesterday.
8. I didn’t become a teacher.
9. He didn’t meet her.
10. We didn’t blame her.

👉Question Form positive:-

1. Did they play a game yesterday?
2. Did you visit your grandmother’s place last week?
3. Did you finish your homework?
4. Did your friend call you yesterday?
5. Did he feel sad yesterday?
6. Did they have dinner last night?
7. Did he meet her?
8. Did you have a pen?
9. Did they go to school yesterday?
10. Did you do your homework?

👉Question Form Negative:-

1. Didn’t they play a game yesterday?
2. Didn’t you visit your grandmother’s place last week?
3. Didn’t you finish your homework?
4. Didn’t your friend call you yesterday?
5. Didn’t he feel sad yesterday?
6. Didn’t they have dinner last night?
7. Didn’t he meet her?
8. Didn’t you have a pen?
9. Didn’t they go to school yesterday?
10. Didn’t you do your homework?

👉Question Form Positive with Question Words:-

1. Why did you go home?
2. What did he do?
3. who did work yesterday?
4. When did he meet her?
5. What time did they go to school?
6. Where did she live?
7. When did you visit your grandmother’s place?
8. Whom did you talk to?
9. Who did she know in the USA?
10. Why did we blame her last week?

👉Question Form Negative with Question Words:-

1. Why didn’t we blame her last week?
2. When didn’t he meet her?
3. Why didn’t you go home?
4. Where didn’t she live?
5. Whom didn’t you talk to?

🛑👇👇👇👇👇👇

Note:- There are three ways to pronounce -ed, depending on the last letter of the verb.

1. Pronounce like \t\ sound: verbs ending in -f, -k, -ss, -ch, -sh, -x

🔸 washed → wɒʃt

🔸 fixed → fɪkst

🔸 kicked → kɪkt

2. Pronounce like \id\: verbs ending in -d or -t

🔸 needed → niːdɪd

🔸 wanted → wɒntɪd

3. Pronounce like \d\ sound: verbs ending in all other letters.

🔸 listened → lɪsᵊnd

🔸 played → pleɪd

Verbs: -

Click the links below to follow other Tenses. Thank you!

Tenses: 👇👇👇

1. Present Tense.

Permanent :

• We live in Hambantota.
• He works at a bank.

Routines :

• I wake up at 6:00.
• I go to sleep at 11:00
  
  Facts :
• The sun rises in the east.
• The sun sets in the west.

Schedule :

• Our class starts at 9:00.
• The flight leaves at noon.

Frequency :

• She always takes the bus.

Singular & Plural Verbs

Most verbs : add [s]

• dance → dances
• cook → cooks
• sleep → sleeps

Verbs ending in s,ss,sh,ch,x,o : add [es]

• wash → washes
• teach → teaches
• fix → fixes
• go → goes
• do → does

Verbs ending in consonant and y : drop [y] add [ies]

• study → studies
• try → tries

Verbs ending in vowel and y : add [s]

• play → plays
• buy → buys

More verbs 1

More verbs 2

Present Continuous / Present Progressive.

✍️ The PRESENT CONTINUOUS is formed with : verb ‘to be’ + verb-ing.

When to use the Present continuous.

1. Now:

• He is sleeping.
• It is raining.

2. Around Now / Unfinished action:

• She is writing a book.
• I am reading a degree.

3. Temporary:

• We are staying at a hotel.
• Julia is working as a waitress.
• John is working as a waiter.

4. Trend:

A trend is something that changing /developing or something that popular.

• The prices of foods are increasing. (changing)
• People are using smart phones. (popular)

5. Repeated action:

• They are always making noise. (negative)

6. Future:

• She is flying to Melbourne next week.
• I am going to teach you.

Spelling for the verb+ing

Most Verbs : add [ing]

• eat → eating
• walk → walking

Verbs ending in e : drop [e] add [ing]

• use → using
• take → taking

Verbs ending in ie : drop [ie] add[y+ing]

• lie → lying
• tie → tying

Verbs ending with Consonant + vowel + Consonant : [double last letter +ing]

• cut → cutting
• clap → clapping

Verbs ending in W,X,Y : add[ing] — not double last letter

• enjoy → enjoying
• fix → fixing

Click the links below to follow other Tenses. Thank you!

Tenses: 👇👇👇

1. Present Tense.
2. Past Tense.

Creating (declaring) variables.

To create a variable must have the type, name and value.

for example:-

🔰In variable creation, there are two parts.

1. Declaration:- the process of defining the variable, along with its type and name.
2. Initialization:- assigning a value

🔰We can create a variable in two ways. such as

1. creating a variable without assigning a value. (Declaration)

Here we specify the data type and provide a name. Later assign a value;

2. create a variable by assigning a value. (Inline initialization)

Here we specify the data type, provide a name, and assign a value in the same line.

Variable types

Local variables:-

👉 Local variables are declared in methods, constructors, or blocks.

👉 These variables will be destroyed once the methods, constructors, or blocks exit the method.

👉 Access modifiers cannot be used for local variables.

👉 Local variables are visible only within the declared method, constructor, or block.

Instance Variables:-

👉 Instance variables are declared outside the methods, constructors or blocks.

👉 Instance variables are created when an object is created.

👉 Access modifiers can be given for instance variables.

👉 Instance variables have default values.

Static / class Variables:-

👉 Class variables are also known as static variables.

👉 Static variables are declared with the static keyword.

👉 Visibility is similar to instance variables.

👉 Static variables can be accessed by calling with the class name.

In Java, an identifier is a name given to a variable, method, class, interface, or any other user-defined item. Identifiers are used to uniquely identify these items within the program.

An identifier in Java must follow these rules:

1. It must begin with a letter, or an underscore (_), or a dollar sign ($).

2. It may be followed by any number of letters, digits, underscores, or dollar signs.

3. It cannot be a keyword reserved by Java (such as “if,” “else,” “while,” etc.).

4. It must not contain spaces or special characters such as !, @, #, %, etc.

Keywords.

In Java, a keyword is a reserved word that has a specific meaning and purpose within the programming language. These words cannot be used as identifiers (variable names, method names, etc.) because they are already reserved by the language for specific purposes.

Examples for some keywords in java:-

Literals.

A literal is a notation that represents a fixed value in source code. In other words, a literal is a specific value that is assigned directly to a variable or used as an argument in an expression, without any computation or evaluation.

There are several types of literals in Java:

• Integer literals: represented by a sequence of digits without a decimal point, optionally preceded by a minus sign (-).
• Floating-point literals: represented by a sequence of digits with a decimal point, optionally preceded by a minus sign, and optionally followed by an exponent indicated by the letter e or E.
• Boolean literals: represented by the keywords true or false.
• Character literals: represented by a single character enclosed in single quotes, such as ‘a’ or ‘\n’.
• String literals: represented by a sequence of characters enclosed in double quotes, such as “Hello, world!”.
• Null literal: represented by the keyword null, used to indicate that a reference variable does not refer to any object.

Read more:- click here 👉Variables

1. Primitive data types.
2. Non-primitive data types.

Non-primitive data types are also known as reference types because they refer to objects.

Examples for non-primitive types: String, Arrays, classes and Interfaces

Java Strings.

Strings are used for storing text.

A String variable contains a collection of characters within double quotes.

Example:-

   String name="Active Heart Association.";

   String email="abc@mail.com";

        System.out.println(name);

        System.out.println(email);

Read more:- Click here 👉 Identifiers, Keywords, Literals

2. A Simple Java Program & analysis of the Java Program

I’m going to use the Notepad application for the first program.

public class FirstProgram{

  //Single-line comment

  /* Multi-line 
     Comments */


   public static void main(String []args){
  
     System.out.println("Hello world!);
 
   }

}

The above program should be saved as FirstProgram.java

🔰Analysis of the Program

1. public: This is providing visibility to all.
2. class: This is used to declare the class in Java.
3. static: Using static keyword that can be accessed without creating the object.
4. void: the return type of the method. void refers to nothing.
5. System.out.println(): print something on the console.
6. public static void main(): This is called main method. It is the startup of a program.

Name of a Java Source File

The name of a source file (.java file/ the file that contains java codes) should be as same as the public class name. Because that is the way to tell the JVM this is the entry point of the program.

Platform Independency

WORA — Write Once Run Anywhere

Data Types:-

Mainly Java data types can be divided into two groups.

1. Primitive data types.
2. Non-primitive data types.

Phases of Java Program

Read more:- click here 👉Java data types.

01. How to install JDK

Step 01: Download the Java Development Kit (JDK). here

Step 02: Open the downloaded .exe file and open.

Step 03: Then click on the Next button.

Step 04: Click on the Next button again.

Step 05: Once you install the java click on the Close button.

Step 06: Set up environment variables in java.

Once you installed JDK on your machine you should get the path of the java bin folder. This folder will exist in one of the folders mentioned in the below image.

There is a folder named java and in this folder, you will see a folder named with the version of JDK. There is a bin folder in this folder. Go to the folder and copy the path.

Step 07: Then right click on “This PC” and select the properties.

Step 08: Click on advance system settings.

Step 09: Click on Environment variables to set the Java runtime environment.

Step 10: Click on the “new” Button of User Variables.

Step 11: Type “PATH” in the variable name

Note: In case you already have a PATH variable created on your PC, click on the “Edit” button. Not the “New” button.

Step 12: Copy the path of the bin folder which is installed in JDK folder.

Step 13: Paste the path of the “bin” folder in the variable value. then click the “OK” button.

Step 14: Then click on the “OK” button of the Environment Variables’ window.

Step 10: Open the Command Prompt “CMD” and type “javac” and press the “Enter” button.

if you see a screen like the below image, Java is installed.

02. How to install IntelliJ IDEA

click here to see how to install IntelliJ IDEA.

Thank you……

Video Resources:

Note: If you don’t have install the JDK on your machine. Please click here to see how to install and setup.

click here to download IntelliJ IDEA.

Step 01: Open the downloaded “.exe” file. Then you will see a window like below. Click on the “Next” button.

Step 2: Choose an appropriate installation location. then Click the “Next” button.

Step 03: Now it will open an installation options window. Select all the required options that are shown on the image below, and click “Next”.

Step 04: Choose the start menu folder as ‘JetBrains’ (by default). Then, click Install.

Step 05: The IntelliJ IDEA will start installing to the system.

Step 06: After the installation, you have to restart your computer to configure the setup. Now when you open IntelliJ IDEA for the first time, you have to accept the Jetbrains community edition terms and click on “Continue”.

The installation is complete.

Thank you…

Video resources:

2nd Step: Open the downloaded (.tgz) file and unzip it. Then copy the unzipped folder into the C drive. Then rename the folder name as “kafka”. (Rename is not nectary)

3rd Step: We need to set some log directories for Zookeeper and Kafka. So we need to make some changes to the server.properties file and zookeeper.properties file. Firstly, open the sever.properties file using the notepad application.

4th Step: change the log.dirs in the server.properties file as follows.

5th Step: change the dataDir in the zookeeper.properties file as follows.

6th Step: Now let's start the zookeeper. So open the CMD from the “C:\kafka” directory. past the below code into the CMD and press enter button.

.\bin\windows\zookeeper-server-start.bat .\config\zookeeper.properties

7th Step: Now let’s start the Kafka server. So again Open the CMD from the “C:\kafka” directory. past the below code into the CMD and press enter button.

.\bin\windows\kafka-server-start.bat .\config\server.properties

Now zookeeper and Kafka servers are configured correctly and running.

Create a new topic:

.\bin\windows\kafka-topics.bat --bootstrap-server localhost:9092 --topic [TOPIC_NAME] --create

View topics:

.\bin\windows\kafka-topics.bat --bootstrap-server=localhost:9092 --list

View Event/Message:

.\bin\windows\kafka-console-consumer.bat --topic order_topics --from-beginning --bootstrap-server localhost:9092

Let’s say you have an application that is a Student Management System with 4 different processes Student registration, Payments, Exam registration, Lecture registration, etc. In a monolithic way, Deploy an application by binding all these processes into a single application. So later, if you wanted to update the Lecture registration or any other process then you have to deploy entire processes because all in one. In this case, you have to make sure all other processes are also error-free by testing. This is not easy when you have a large scale of applications. Therefore, microservices came into the industry.

Microservice Architecture.

There is no single definition of microservices. But let's go through some comprehendible descriptions to comprehend.

Microservices, also known as Microservice architecture. It implements layered architecture. It allows building applications by isolating business processes for a business goal then it becomes loosely coupled. The microservices follow the UNIX philosophy of “Do one thing and do it well”.

Let’s take our previous example which is the student management system. Under microservice architecture, Instead of a coalesced single module in the monolithic architecture, all the services are spread into individual modules. These microservices (individual modules) are capable to communicate with each other. See the below diagram...

Characteristics of Microservices

Microservices have a dedicated purpose for living. In other words, it is a domain-driven development. It has to have an exactly defined scope. More than that, there are a few characteristics such as,

• Run own processes (Own web container)
• Communicate with other services via a lightweight mechanism. Most of the time it uses HTTP as well as it isn’t limited to HTTP.
• Scale and deploy as individual services.
• It should maintain decentralized control as much as possible.

Independently scalable

This is one of the key features of microservices. According to “The Art of Scalability” (book) they have introduced the AKF scale cube for a better understanding of scaling. They are using Rubic’s cube to introduce the AKF scale.

Using this, they have introduced three axes which are the x-axis, y-axis, and z-axis.

X-axis scaling:- An application should be able to scale out through the x-axis. That means if one instance is not enough you should be able to create other instances and keep running. Sometimes we can do clustering, adding more data centers, etc. However, you should be able to scale out.

Z-axis scaling:- Through this z-axis should be able to sharding and also should be able to geographically split out the traffic. For example, European customers are direct to European servers, and Asian customers are direct to Asian servers, etc.

Y-axis scaling:- Through this y-axis, It should be able to do functional decomposition.

There is no restriction to selecting any programming language to develop an application under microservice architecture. but Java, Python, and javascript are the most popular programming languages for developing microservices.

It is very important to use domain-driven design when you consider the design. You should make sure, your one service should not depending on any factors. That means, your service should be able to unplug at any given time from the system and plug in at any given time from the system. That doesn’t mean your system should be able to run without your service. It means your services should be loosely coupled.

More than that, There are the most important parts of microservices are service resilience and fault tolerance. This is not a feature but you must implement that. For example, let’s assume you have two different services “A” and “B”. let’s say, you're going to invoke “service B” from “Service A”. Now “service B” is time out or not working. therefore, now you should be able to maintain this failure situation. That calls fault tolerance. There are multiple ways that you can do this. you can use a failure mechanism, you can have a proxy or you can have the circuit breaker pattern.

Advantages

• Microservices are self-contained, independent deployment modules.
• The cost of scaling is comparatively less than monolithic architecture.
• Dynamic scaling.
• Fewer dependencies and easy to test.
• Microservices follow the single responsibility principle.

Disadvantages

• Difficult to manage a large number of services.
• Complex testing over a distributed environment.
• This has all the associated complexities of the distributed system.

Let’s see another article called design patterns for Microservice.

Thank you…