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_01_basics/Datatypes.java

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+package com._01_basics;
+
+public class Datatypes {
+    public static void main (String[] args) {
+        int myNum = 5;               // Integer (whole number)
+        float myFloatNum = 5.99f;    // Floating point number
+        char myLetter = 'D';         // Character
+        boolean myBool = true;       // Boolean
+        String myText = "Hello";     // String
+
+
+        System.out.println("These below are the datatypes : ");
+        System.out.println("Integer Value = "+myNum);
+        System.out.println("Integer Value = "+myFloatNum);
+        System.out.println("Integer Value = "+myLetter);
+        System.out.println("Integer Value = "+myBool);
+        System.out.println("Integer Value = "+myText);
+
+    }
+}
+
+//Primitive Datatypes in Java
+
+/*
+
+
+Data Type	Size	  Description
+byte	    1 byte	  Stores whole numbers from -128 to 127
+short	    2 bytes	  Stores whole numbers from -32,768 to 32,767
+int	        4 bytes	 Stores whole numbers from -2,147,483,648 to 2,147,483,647
+long	    8 bytes	  Stores whole numbers from -9,223,372,036,854,775,808 to 9,223,372,036,854,775,807
+float	    4 bytes	  Stores fractional numbers. Sufficient for storing 6 to 7 decimal digits
+double	    8 bytes	  Stores fractional numbers. Sufficient for storing 15 decimal digits
+boolean	    1 bit	  Stores true or false values
+char	    2 bytes	  Stores a single character/letter or ASCII values
+
+ */

_01_basics/Main.java

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+package com._01_basics;
+
+public class Main {
+
+    public static void main(String[] args) {
+        System.out.println("Hello World");
+    }
+}
+// This is a single line comment in java
+
+/*
+This is
+a multiline comment
+in java
+*/

_01_basics/Operators.java

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+package com._01_basics;
+import java.util.Scanner;
+public class Operators {
+    public static void main (String[] args) {
+        int x,y,sum,sub,mul,div,mod;
+        Scanner inp = new Scanner(System.in);
+        System.out.println("Enter value of x");
+        x = inp.nextInt();
+        System.out.println("Enter value of y");
+        y = inp.nextInt();
+        sum = x + y;
+        sub = x - y;
+        mul = x * y;
+        div = x / y;
+        mod = x % y;
+        System.out.println("Sum = "+sum);
+        System.out.println("Sum = "+sub);
+        System.out.println("Sum = "+mul);
+        System.out.println("Sum = "+div);
+        System.out.println("Sum = "+mod);
+    }
+}

_01_basics/StringMethods.java

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+package com._01_basics;
+
+public class StringMethods {
+    public static void main (String[] args) {
+        String greeting = "Hello";
+        System.out.println(greeting+" Sahil");
+
+        //Function to get string length
+        String txt = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
+        System.out.println("The length of the txt string is: " + txt.length());
+
+        //String to UPPERCASE
+        String words = "Hello World";
+        System.out.println(words.toUpperCase());
+        //String to lowercase
+        System.out.println(words.toLowerCase());
+
+        //Finding a Character in a String
+        String text = "Please locate where 'sb' occurs";
+        System.out.println("sb is at "+text.indexOf("sb")+"th location");
+
+        //String Concatenation +
+        String firstName = "Sahil";
+        String lastName = "Batra";
+        System.out.println("My name is "+firstName+" "+lastName);
+
+        //String Concatenation using concat() method
+        System.out.println(firstName.concat(lastName)+" is my name.");
+
+        //Special Characters
+        /*
+        Escape character	Result	Description
+        \'	                '	    Single quote
+        \"	                "       Double quote
+        \\	                \	    Backslash
+         */
+        String desc = "We are the so-called \"Punjabi\" from the north.";
+        System.out.println(desc);
+        String text1 = "It\'s alright";
+        System.out.println("Dont worry "+text1);
+
+        //Six other escape sequences are valid in Java:
+        /*
+        Code	Result
+        \n 	    New Line
+        \r	    Carriage Return
+        \t	    Tab
+        \b	    Backspace
+        \f	    Form Feed
+        Try above yourself
+         */
+
+        //WARNING!
+        //Java uses the + operator for both addition and concatenation.
+        //Numbers are added. Strings are concatenated.
+    }
+}

_01_basics/Typecasting.java

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+package com._01_basics;
+
+public class Typecasting {
+    public static void main(String[] args) {
+
+        //Widening Casting
+
+        int myInt = 9;
+        double myDouble = myInt; // Automatic casting: int to double
+
+        System.out.println(myInt);      // Outputs 9
+        System.out.println(myDouble);   // Outputs 9.0
+
+        //Narrowing Casting
+
+        double myDoublen = 9.78d;
+        int myIntn = (int) myDouble; // Manual casting: double to int
+
+        System.out.println(myDouble);   // Outputs 9.78
+        System.out.println(myInt);      // Outputs 9 but still its a wrong practise
+    }
+}

_01_basics/Variables.java

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+package com._01_basics;
+
+public class Variables {
+    public static void main (String[] args) {
+        String myName = "Sahil";
+        int Num = 15;  // declaration with initialization
+        Num = 20;  // initialization afterwards
+        System.out.println(Num);
+        final int myConst = 30;
+        System.out.println(myConst);
+        //myNum = 25;  // will generate an error: cannot assign a value to a final variable
+
+        // other data types
+
+        int myNum = 5;
+        float myFloatNum = 5.99f;
+        char myLetter = 'D';
+        boolean myBool = true;
+        String myText = "Hello";
+
+        System.out.println("Integer Value = "+myNum);
+        System.out.println("Integer Value = "+myFloatNum);
+        System.out.println("Integer Value = "+myLetter);
+        System.out.println("Integer Value = "+myBool);
+        System.out.println("Integer Value = "+myText);
+
+        // For numeric values, the + character works as a mathematical operator
+        int x = 5;
+        int y = 6;
+        System.out.println(x + y); // Print the value of x + y
+
+        // Declare Many Variables
+        int a = 5, b = 6, c = 50;
+        System.out.println(a + b + c);
+        System.out.println(a+ "" +b+ "" +c);
+    }
+}
+
+// variable declaration :
+// data type variable_name = value;
+/* you can add the final keyword if you don't want others
+(or yourself) to overwrite existing values
+(this will declare the variable as "final" or "constant",
+which means unchangeable and read-only */
+// Here x. y , a,b myNum and more of these are called java identifiers

_02_control_statements/BreakAndContinue.java

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+package com._02_control_statements;
+
+public class BreakAndContinue {
+    public static void main(String[] args) {
+        System.out.println("Breaking at 4 but loop is till 10");
+        for (int i = 0; i <= 10; i++) {
+            if (i == 4) {
+                break;
+            }
+            System.out.println(i);
+        }
+        System.out.println("\nContinuing at 4 but loop is till 10");
+        for (int j = 0; j < 10; j++) {
+            if (j== 4) {
+                continue;
+            }
+            System.out.println(j);
+        }
+    }
+}

_02_control_statements/Enhanced_Switch.java

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+package com._02_control_statements;
+
+import java.util.Scanner;
+// Shorthand Switch Statement
+public class Enhanced_Switch {
+    public static void main(String[] args) {
+        Scanner inp = new Scanner(System.in);
+        String fruit = inp.next();
+
+        switch (fruit) {
+            case "Mango" -> System.out.println("King of fruit");
+            case "Apple" -> System.out.println("A sweet red fruit");
+            case "Orange" -> System.out.println("A round fruit");
+            case "Grapes" -> System.out.println("Small green fruit");
+            default -> System.out.println("Please enter a valid food");
+        }
+    }
+}

_02_control_statements/For.java

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+package com._02_control_statements;
+
+public class For {
+    public static void main(String[] args) {
+        System.out.println("Loop from 0 to 5");
+        for (int i = 0; i <= 5; i++) {
+            System.out.println(i);
+        }
+        System.out.println("Loop for even numbers 0 to 10");
+        for (int j = 0; j <= 10; j = j + 2) {
+            System.out.println(j);
+        }
+        //Using for loop with array
+        String[] cars = {"Volvo", "BMW", "Ford", "Mazda"};
+        for (String k : cars) {
+            System.out.println(k);
+        }
+    }
+}

_02_control_statements/IfElse.java

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+package com._02_control_statements;
+
+public class IfElse {
+    public static void main (String[] args) {
+        //if statement
+        if (20 > 18) {
+            System.out.println("20 is greater than 18");
+        }
+        int x = 20;
+        int y = 18;
+        if (x > y) {
+            System.out.println("x is greater than y");
+        }
+        //if else statement
+        int time = 20;
+        if (time < 18) {
+            System.out.println("Good day.");
+        } else {
+            System.out.println("Good evening.");
+        }
+        //else if statement
+        int t = 22;
+        if (t < 10) {
+            System.out.println("Good morning.");
+        } else if (t < 20) {
+            System.out.println("Good day.");
+        } else {
+            System.out.println("Good evening.");
+        }
+        //Short Hand if..else (Ternary Operator)
+        int timezone = 20;
+        String result = (timezone < 18) ? "Good day." : "Good evening.";
+        System.out.println(result);
+    }
+}