DEV Community: Dev From Legacy

Git and Github: a fast sequence

Dev From Legacy — Thu, 17 Sep 2020 03:37:06 +0000

You can practice the steps in sequence:

Starting: download and install Git, then you can open Git Bash.
Creating a repository: access a diretory with some source code (example: test.html) and type git init.
Adding files: at same directory, you can type: git add . . Then all files in that directory will be added.
Checking status: type git status and you will see the message: Changes to be committed.
Configure your user: execute the commands bellow changing data between quotation marks.

git config --global user.email "you@example.com"
git config --global user.name "Your Name"

Committing: execute the commands bellow changing message between quotation marks.

git commit -m "Your message."

Visualizing logs: type git log .
Ignoring files: you can create a empty file and it adds filename in a file called .gitigonore at same directory.
Starting with Github: Create a account in Github and create a new repository.
Adding remote repository: type code bellow changing your repository link.

git remote add origin https://github.com/YOURNAME/NAMEREPOSITORY.git

Pushing your code: type git push origin master and enter your login and password.
Cloning from Github: you can access a different directory in your computer and execute the command bellow.

git clone https://github.com/YOURNAME/NAMEREPOSITORY.git

Pulling from Github: you can change a file on Github page, then execute the command bellow.

git pull https://github.com/YOURNAME/NAMEREPOSITORY.git master

Creating new branch: git branch NAMEBRANCH.
Switching branch: git checkout NAMEBRANCH.
Committing on branch: change any file and execute commands bellow.

git add NOMEFILE
git commit -m "Changing file for commit branch test."

Merging: execute commands bellow.

git checkout master
git merge NAMEBRANCH

Rebase: change any file and execute steps bellow.

git add NOMEFILE
git commit -m "Changing file for commit master for rebase test."
git checkout NAMEBRANCH

Change any file again.

git add NOMEFILE
git commit -m "Changing file for commit branch for rebase test."
git checkout master
git rebase NAMEBRANCH

Reseting and restoring: change any file and execute steps bellow.

git add NOMEFILE
git reset HEAD NOMEFILE
git checkout -- NOMEFILE

Reverting: change any file and execute steps bellow.

git add NOMEFILE
git commit -m "Changing file for revert test."
git log

You should get the hash related the last commit.

git revert HASHLASTCOMMIT

Stash: change any file and execute steps bellow, the command git stath pop will remove from stash list and apply, then you can commit.

git stash
git stash pop
git add NOMEFILE
git commit -m "Changing file for stash test."

Switching to a different commit and creating a branch: execute steps bellow.

git log --oneline

Get a hash any past commit.

git checkout HASHPASTCOMMIT
git checkout -b NOMENEWBRANCH

Difference between commits: return to master git checkout master and execute steps bellow.

git log --oneline

Get two hash from any commits.

git diff HASH1..HASH2

Creating tag: execute steps bellow.

git tag -a VERSIONNAME -m "Creating a tag."

You can push commits and tag to Github.

git push origin master
git push origin VERSIONNAME

Any feedback is welcome!

Java first steps: 20 things I'd forgotten

Dev From Legacy — Wed, 16 Sep 2020 02:01:35 +0000

If you don't work with Java or you're relearning it (like me!), I'm sharing some things:

1. Java Major features: Object Oriented, Platform independent, it has many libraries and it's similar to C++.

2. Java Virtual Machine(JVM): Java source code [.java] is compiled into Java bytecode [.class], which is executed by a Java virtual machine (JVM).

3. Important Versions: 1 [1995], 5 [2004] and 8 [2014]. Current version in 2020-09: 9.

4. Java Kit Development: it includes the Java Runtime Environment (JRE), an interpreter/loader (Java), a compiler (javac), an archiver (jar), a documentation generator (Javadoc) and other tools needed in Java development.

5. Environment Variables: unless on Windows, you will need to set environment variable.

6. Compiling/Executing Java on Command Prompt: you can compile your .java program using javac MyProgram.java and you can run using java MyProgram.

7. Best options IDE for Java: currently Eclipse, Netbeans and IntelliJ IDEA.

8. Java Hello World: in the Java programming language, every application must contain a main method whose signature is: public static void main(String[] args).

class HelloWorldProgram {
    public static void main(String[] args) {
        System.out.println("Hello World!"); // Display the string.
    }
}

9. Java Comments: Single-line comments start with two forward slashes // and multi-line comments start with /* and ends with */

10. Java naming convention - CamelCase: Java follows camel-case syntax for naming the class, interface, method and variable. Method and variable should start with lowercase letter (example: ImageSprite ). Class and interface should start with uppercase letter (example: getBackground ).

*11. Java Operators: *

Arithmetic [+, -, *, /, %, ++, --]
Logical [&&, ||, !]
Comparison [==, !=, >, <, >=, <=, >>=, <<=]
Assignment [=, +=, -=, *=, /=, %=, &=, |=, ^=]

12. Concatenation by +: using operator + is one way to build a string in Java.

public class TestVariables {

    public static void main(String args[]) {

        int age = 30;
        System.out.println("Age: " + age);
    }
}

13. Floating-Point Data Types: Java has some peculiarities about floating-point, like the outputs below.

public class TestFloatingPoint {

    public static void main(String args[]) {

        double salary = 1250.70;
        System.out.println("S: " + salary); //Output: S: 1250.7
        double division = 3.14 / 2;
        System.out.println(division); //Output: 1.57
        int otherDivision = 5 / 2;
        System.out.println(otherDivision); //Output: 2
        double newDivision = 5 / 2;
        System.out.println(newDivision); //Output: 2.0
        double lastDivision = 5.0 / 2;
        System.out.println(lastDivision); //Output: 2.5
        double number1 = 0.2;
        double number2 = 0.1;
        System.out.println(number1 +number2);
        //Output: 0.30000000000000004
    }
}

14. Java Type Casting/Conversion: Java Type Casting is classified into two types: Explicit and Implicit.

public class TestConversion {

    public static void main(String[] args) {

        //Implicit casting
        byte a = 40;
        short b = a;
        int c = b;
        long d = c;
        float e = d;
        double f = e;
        System.out.println("byte : "+a); //Output: 40 
        System.out.println("short : "+b); //Output: 40
        System.out.println("int: "+c); //Output: 40
        System.out.println("long: "+d); //Output: 40
        System.out.println("float: "+e); //Output: 40.0
        System.out.println("double: "+f); //Output: 40.0

        //Explicit casting
        double g = 30.0;
        float h = (float) g;
        long i = (long) h;
        int j = (int) i;
        short k = (short) j;
        byte l = (byte) k;
        System.out.println("double: "+g); //Output: 30.0
        System.out.println("float: "+h); //Output: 30.0
        System.out.println("long: "+i); //Output: 30
        System.out.println("int: "+j); //Output: 30
        System.out.println("short: "+k); //Output: 30
        System.out.println("byte: "+l); //Output: 30
    }
}

15. Characters and Strings in Java: you can see some examples bellow.

public class TestCharacters {

    public static void main(String args[]) {
        char letter = 'a';
        System.out.println(letter); //Output: a
        char letterValue = 65;
        System.out.println(letterValue); //Output: A
        char nextLetterValue = (char) (letterValue + 1);
        System.out.println(nextLetterValue); //Output: B
        String sentence = "String test";
        System.out.println(sentence); //Output: String test
        String newSentence = "String test" + 1;
        System.out.println(newSentence); //Output: String test1
    }
}

16. Conditionals in Java: you can see some examples bellow.

public class TestConditional {

    public static void main(String[] args) {

        int age = 22;
        int numberPeople = 1;
        boolean accompanied = (numberPeople > 1);
        if ((age >= 21 || accompanied) && numberPeople < 20) {
            System.out.println("You are allowed!");
            switch (numberPeople) {
                case 1:
                    System.out.println("Table for 1 on the right!");
                    break;
                case 2:
                    System.out.println("Table for 2 on the left!");
                    break;
                default:
                    System.out.println("Table for group on the patio!");
            }
        } else {
            System.out.println("You arent't allowed!");
        }
        // Output: You are allowed!
        // Table for 1 on the right!
    }
}

17. Scope: A block of code refers to all of the code between curly braces {}.

public class TestScope {
    public static void main(String[] args) {

        { // This is a block
            int x = 100;
            // Code here CAN use x
            System.out.println(x);

        } // The block ends here
        // Code here CANNOT use x
    }
}

18. Loops in Java: you can see some examples bellow.

public class TestLoop {

    public static void main(String[] args) {
        int counter = 0;
        while(counter <= 1) {
            System.out.println(counter);
            counter++;
        }
        System.out.println(counter);

        for(int newCounter = 0; newCounter <= 1; newCounter++) {
            System.out.println(newCounter);
        }
        //Output: 0 1 2 0 1
    }
}

19. Break/continue:

public class TestBreakContinue {

    public static void main(String[] args) {
        for (int i = 0; i < 4; i++) {
            if (i == 2) {
                break;
            }
            System.out.println(i);
        }
        // Output: 0 1

        for (int i = 0; i < 4; i++) {
            if (i == 2) {
                continue;
            }
            System.out.println(i);
        }
        // Output: 0 1 3
    }
}

20. Arrays in Java: you can see some examples bellow.

public class TestArrays {

    public static void main(String[] args) {

        String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
        System.out.println(cars[0]);
        // Outputs Volvo        
    }
}