Updated: Wed, 6-17-20,  Mon, 6-15-20,   @11:45pm b4 midnite
         Tue, 6-09-20,  Fri, 5-29-20,   Thu, 5-28-20 @10:45pm     // Note: Tue, 6-9-20 2:08am; started at past midnite
         Tue, 05-26-20  Mon, 05-25-20   Sat, 04-16-20   Wed, 02-12-20

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>> add to network notes >> adding userss and domain thru DosCmds  >>  1337red.wordpress.com/building-and-attacking-an-active-directory-lab-with-powershell/

Java Pgming Notes:

Format:

https://www.jdoodle.com/online-java-compiler/ 

    Html Editor for everyone
https://www.qhmit.com/html/online-html-editor/full/

  Good authors / teachers / video for java pgming
-Caleb
-Awaiz Mirza
-Mike Dane
-Eli Computer guy (Network, DNS, Active Directory, etc)
-java sample mini pgms
-Nam Minh - viet java guru
-

  ** java mini sample codes
https://projectsgeek.com/2014/07/link-handler-system-project-in-java.html#comment-224098

  Essential to learn the syntax

------ another reader pgm >> t3.java --------

// reader pgm

import java.io.File;                             // Import the File class
import java.io.FileNotFoundException;            // Import this class to handle errors
import java.util.Scanner;                        // Import the Scanner class to read text files

public class t3 {                                // call your t3 read pgm
  public static void main(String[] args) {
    try {
      File myObj = new File("d:\\TEMP3.txt");    // put your file name here! ; note double \\
      Scanner myReader = new Scanner(myObj);
      while (myReader.hasNextLine()) {
        String data = myReader.nextLine();       // read each line
        System.out.println(data);                // display each line 
      }
      myReader.close();
    } catch (FileNotFoundException e) {          // use exception if File not found!!
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}

// end of reader pgm; working one.   It will read txt file and output whatever in it. 

-----------------

Ssmple9:  reading file

Create a File

To create a file in Java, you can use the createNewFile() method. This method returns a boolean value: true if the file was successfully created, and false if the file already exists. Note that the method is enclosed in a try...catch block. This is necessary because it throws an IOException if an error occurs (if the file cannot be created for some reason):

import java.io.File;  // Import the File class
import java.io.IOException;  // Import the IOException class to handle errors

public class CreateFile {
  public static void main(String[] args) {
    try {
      File myObj = new File("filename.txt");
      if (myObj.createNewFile()) {
        System.out.println("File created: " + myObj.getName());
      } else {
        System.out.println("File already exists.");
      }
    } catch (IOException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}

======

Write To a File

In the following example, we use the FileWriter class together with its write() method to write some text to the file we created in the example above. Note that when you are done writing to the file, you should close it with the close() method:

import java.io.FileWriter;   // Import the FileWriter class
import java.io.IOException;  // Import the IOException class to handle errors

public class WriteToFile {
  public static void main(String[] args) {
    try {
      FileWriter myWriter = new FileWriter("filename.txt");
      myWriter.write("Files in Java might be tricky, but it is fun enough!");
      myWriter.close();
      System.out.println("Successfully wrote to the file.");
    } catch (IOException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}

import java.io.File;  // Import the File class
import java.io.FileNotFoundException;  // Import this class to handle errors
import java.util.Scanner; // Import the Scanner class to read text files

public class ReadFile {
  public static void main(String[] args) {
    try {
      File myObj = new File("filename.txt");
      Scanner myReader = new Scanner(myObj);
      while (myReader.hasNextLine()) {
        String data = myReader.nextLine();
        System.out.println(data);
      }
      myReader.close();
    } catch (FileNotFoundException e) {
      System.out.println("An error occurred.");
      e.printStackTrace();
    }
  }
}

To get more information about a file, use any of the File methods:

import java.io.File;  // Import the File class

public class GetFileInfo { 
  public static void main(String[] args) {
    File myObj = new File("filename.txt");
    if (myObj.exists()) {
      System.out.println("File name: " + myObj.getName());
      System.out.println("Absolute path: " + myObj.getAbsolutePath());
      System.out.println("Writeable: " + myObj.canWrite());
      System.out.println("Readable " + myObj.canRead());
      System.out.println("File size in bytes " + myObj.length());
    } else {
      System.out.println("The file does not exist.");
    }
  }
}

The output will be:

======

sample8:  String format() method

Example of Java String format() method

note that %s, for string, %.6f for number with decimals

%s – for strings
%f – for floats
%d – for integers

public class Example{  
   public static void main(String args[]){  
	String str = "just a string";  
		
	//concatenating string using format
	String formattedString = String.format("My String is %s", str);  
		
	/*formatting the  value passed and concatenating at the same time
	 * %.6f is for having 6 digits in the fractional part
	 */
	String formattedString2 = String.format("My String is %.6f",12.121);

	System.out.println(formattedString); 
	System.out.println(formattedString2);  
   }
}

Output:

My String is just a string
My String is 12.121000

--------

sample 8a:  Format method

public class JavaExample {  
   public static void main(String[] args) {  
	String str1 = String.format("%d", 15); // Integer value  
	String str2 = String.format("%s", "BeginnersBook.com"); // String  
	String str3 = String.format("%f", 16.10); // Float value  
	String str4 = String.format("%x", 189);  // Hexadecimal value  
	String str5 = String.format("%c", 'P');  // Char value  
	String str6 = String.format("%o", 189); // Octal value
	System.out.println(str1);  
	System.out.println(str2);  
	System.out.println(str3);  
	System.out.println(str4);  
	System.out.println(str5);  
	System.out.println(str6); 
   }  
}

Output:
15
BeginnersBook.com
16.10000
bd
P
275

Java String Format Specifiers

%c – Character
%d – Integer
%s – String
%o – Octal
%x – Hexadecimal
%f – Floating number
%h – hash code of a value

-----

Sample7:  >> Array, Loop, var declaration for Int and String

Enhanced for loop is useful when you want to iterate Array/Collections, it is easy to write and understand.

Let’s take the same example that we have written above and rewrite it using enhanced for loop.

class ForLoopExample3 {
   public static void main(String args[]){
      int arr[]={2,11,45,9};
      for (int num : arr) {
         System.out.println(num);
      }
   }
}

Output:

2
11
45
9

Note: In the above example, I have declared the num as int in the enhanced for loop. This will change depending on the data type of array. For example, the enhanced for loop for string type would look like this:

String arr[]={"hi","hello","bye"};
for (String str : arr) {
         System.out.println(str);
}

-----

sample2a:  loop using increments

Simple For loop

class ForLoopExample {
    public static void main(String args[]){
         for(int i=5; i>1; i--){
              System.out.println("The value of i is: "+i);
         }
    }
}

The output of this program is:

The value of i is: 5
The value of i is: 4
The value of i is: 3
The value of i is: 2

----

sample6: 

StringIndexOutOfBound Exception

Class: Java.lang.StringIndexOutOfBoundsException

• An object of this class gets created whenever an index is invoked of a string, which is not in the range.
• Each character of a string object is stored in a particular index starting from 0.
• To get a character present in a particular index of a string we can use a method charAt(int) of java.lang.String where int argument is the index.

E.g.

class ExceptionDemo4
{
   public static void main(String args[])
   {
      try{
	 String str="beginnersbook";
	 System.out.println(str.length());;
	 char c = str.charAt(0);
	 c = str.charAt(40);
	 System.out.println(c);
      }catch(StringIndexOutOfBoundsException e){
	  System.out.println("StringIndexOutOfBoundsException!!");
       }
   }
}

Output:

13
StringIndexOutOfBoundsException!!

-----------------

sample7:  exception catching

-discussion in >> https://stackoverflow.com/questions/39849984/what-is-a-numberformatexception-and-how-can-i-fix-it

soltn:

try {
    i = Integer.parseInt(myString);
} catch (NumberFormatException e) {
    e.printStackTrace();
    //somehow workout the issue with an improper input. It's up to your business logic.
}

to issue with the other code: it gotten some errors

Error Message:
Exception in thread "main" java.lang.NumberFormatException: For input string: "Ace of Clubs"
    at java.lang.NumberFormatException.forInputString(NumberFormatException.java:65)
    at java.lang.Integer.parseInt(Integer.java:580)
    at java.lang.Integer.parseInt(Integer.java:615)
    at set07102.Cards.main(Cards.java:68)
C:\Users\qasim\AppData\Local\NetBeans\Cache\8.1\executor-snippets\run.xml:53: Java returned: 1
BUILD FAILED (total time: 0 seconds)

---

My While Loop:

while (response != 'q' && index < 52) {
    System.out.println(cards[index]);
    int first_value = Integer.parseInt(cards[index]);
    int value = 0;
    //Add a Scanner
    Scanner scanner = new Scanner(System.in);
    System.out.println("Will the next card be higher or lower?, press q if you want to quit");
    String guess = scanner.nextLine();
    if(cards[index].startsWith("Ace")) { value = 1; }
    if(cards[index].startsWith("2")) { value = 2; }
    if(cards[index].startsWith("3")) { value = 3; }
    //checking 4-10
    if(cards[index].startsWith("Queen")){ value = 11; }
    if(cards[index].startsWith("King")){ value = 12; }
    if(guess.startsWith("h")){
        if(value > first_value){ System.out.println("You answer was right, weldone!"); } 
        else { System.out.println("You answer was wrong, try again!"); }
    } else if(guess.startsWith("l")){
        if(value < first_value) { System.out.println("You answer as right, try again!"); }
        else { System.out.println("You answer was wrong, try again!"); }
    } else { System.cut!!

Fin

** end ** ----------------- fin ---------------------