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Commit 0d2c181

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‎src/A_01_Primitive_Data_Types.java‎

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public class A_01_Primitive_Data_Types {
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public static void main(String[] args) {
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// In front of every datatypes there must be a Variable (e.g: int x = 1, where x is the Variable)
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// Integers
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System.out.println("Integers");
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byte b = 10;
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short s = 20;
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int i = -30;
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long l = 1000;
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System.out.println(b);
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System.out.println(s);
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System.out.println(i);
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System.out.println(l);
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// Floating Point
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System.out.println("Floating Point");
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float f = 10.54f;
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double d = 20.12;
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System.out.println(f);
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System.out.println(d);
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System.out.println(f+d);
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// Character
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System.out.println("Characters");
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char ch = 'A';
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System.out.println(ch);
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// Boolean
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System.out.println("Boolean");
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boolean bool = true;
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boolean flag = false;
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System.out.println(bool);
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System.out.println(flag);
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}
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}
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public class A_02_Identifiers_Variable_Rules {
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public static void main(String[] args) {
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// keyboard tip: Alt + z = To view all the contents
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// keyboard tip: Ctrl + / = Comment a line
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// Rules:
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// 1) Variable Names can contain letters, digits, underscores, and dollar signs
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// 2) Variable Names must begin with a letter, $ or _ (doesn't matter Uppercase or Lowercase)
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// 3) Variable Names best practice should start with lowercase letter, and cannot contain whitespace
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// 4) Variable Names are case-sensitive (e.g: "Name" and "name" are different variables)
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// 5) Reserved words like Java keywords (e.g: int, boolean, char) cannot be used as Variable Names.
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int a_1$ = 10;
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int A_1$ = 10;
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// as you can see there is an error as it has a white spacing in between.
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// int a_ 3$ = 10;
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System.out.println(a_1$);
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System.out.println(A_1$);
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// this file will not run as there is an error
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// System.out.println(a_ 3$);
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// similarly there will be an error cause you cannot use reserved words as Variable Names.
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// String int = 'Hello World!'
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// int String = 10;
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// however, why does it work for this? It's cause the string is not a data type keyword *String* is not string. Hence, it why Java is case sensitive.
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int string = 10;
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System.out.println(string);
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}
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}

‎src/A_03_Type_Casting.java‎

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public class A_03_Type_Casting {
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// Implicit Type Casting (automatic by compiler)
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// byte -> short -> char -> int -> long -> float -> double
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// Explicit Type Casting
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// double -> float -> long -> int -> char -> short -> byte
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public static void main(String[] args) {
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// Implicit
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int number1 = 10;
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double number2 = number1;
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System.out.println(number2);
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// Explicit
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double num1 = 20.44;
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int num2 = (int)num1;
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System.out.print(num2);
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}
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}

‎src/A_04_Arithmetic_Operators.java‎

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public class A_04_Arithmetic_Operators {
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public static void main(String[] args) {
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// using the '+' operator you can join 2 Variable string together as shown below
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String msg1 = "Hello World!";
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String msg2 = "My name is Ang Jianming.";
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System.out.println(msg1 + " " + msg2);
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// Arithmetic Operator (+, -, *, /, %)
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int a = 10;
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int b = 20;
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int c = a + b; // Addition
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System.out.println(c);
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int d = a - b; // Subtraction
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System.out.println(d);
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int e = a * b; // Multiply
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System.out.println(e);
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int f = b / a; // Divide
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System.out.println(f);
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int g = a % b; // Modulus
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System.out.println(g);
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}
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}

‎src/A_05_User_Input.java‎

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/*
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* Author AngJianming
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*
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*/
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// it is a must to import java.util.Scanner; to access some external files which has the functionality to read input from the console. In Java this is the way to get certain functionalities which is not build in therefore, needing to import them.
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import java.util.Scanner;
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public class A_05_User_Input {
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public static void main(String[] args) {
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Scanner user_input = new Scanner(System.in);
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System.out.print("Enter your name: ");
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String name = user_input.nextLine();
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System.out.println("My name is " + name);
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// Example Calculator
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Scanner scanner = new Scanner(System.in);
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// Prompt the user to enter the first number
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System.out.print("Enter the first integer: ");
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int x = scanner.nextInt();
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// Prompt the user to enter the second number
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System.out.print("Enter the second integer: ");
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int y = scanner.nextInt();
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// Perform arithmetic operations
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int sum = x + y; // Addition
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int difference = x - y; // Subtraction
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int product = x * y; // Multiplication
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// To handle division by zero, you can check if b == 0
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// but for simplicity, we assume b != 0 in this example
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double quotient = (double) x / y; // Division
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int modulus = x % y; // Modulus (remainder)
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// Print the results
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System.out.println("\n--- Results ---");
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System.out.println(x + " + " + y + " = " + sum);
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System.out.println(x + " - " + y + " = " + difference);
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System.out.println(x + " ×ばつ " + y + " = " + product);
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System.out.println(x + " ÷ " + y + " = " + quotient);
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System.out.println(x + " % " + y + " = " +"R"+ modulus);
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// Close the scanner
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scanner.close();
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}
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}

‎src/B_01_Assignment_Operators.java‎

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public class B_01_Assignment_Operators {
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public static void main(String[] args) {
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// Assignment Operators (=, +=, -=, /=, *=)
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int a = 10;
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int b = 5;
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a += b; // meaning a = a+b or a = 10+b
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System.out.println(a);
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// a = 15 this should be the expected result
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a -= 2; // meaning a = a-2;
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System.out.println(a);
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a /= 2; // meaning a = a/2
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System.out.println(a);
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a *= 2; // meaning a = a*2
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System.out.println(a);
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a %= 5; // meaning a = a%5
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System.out.println(a);
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}
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}

‎src/B_02_Relational_Operators.java‎

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public class B_02_Relational_Operators {
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// ture, false (boolean)
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// Relational Operators ( ==, !=, <, >, <=, >=)
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public static void main(String[] args) {
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int a = 10;
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int b = 15;
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System.out.println(a == b); // if a is equal to b true, otherwise false
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System.out.println(a != b); // 10 is not equal to 15 true, otherwise false
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System.out.println(a < b); // 10 is less than 15 true, otherwise false
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System.out.println(b > a); // 10 is more than 15 true, otherwise false
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System.out.println(a <= b); // 10 is less or equal to 15 true, otherwise false
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System.out.println(b >= a); // 10 is more than or equal to 15 true, otherwise false
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// 10 is less than, or equal to 10 true, otherwise false.
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System.out.println(10 < 10); // is false because it cannot 10 cannot be less than 10
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System.out.println(10 <= 10); // is true because it can be less than or EQUAL to 10 (Keyword 'equal')
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System.out.println(10 > 10); // is false because it cannot 10 cannot be more than 10
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System.out.println(10 >= 10); // is true because it can be more than or EQUAL to 10 (Keyword 'equal')
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}
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}

‎src/B_03_Logical_Operators.java‎

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import java.security.spec.RSAOtherPrimeInfo;
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public class B_03_Logical_Operators {
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public static void main(String[] args) {
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// Logical Operator ( &&, ||, !)
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// AND (&&) - is all condition is true then return true.
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// true && true = true
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// true && false = false
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// false && true = false
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// false && false = false
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System.out.println(10>5);
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System.out.println(20>14);
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System.out.println((10>5) && (20>14));
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// OR (||) - if any condition is true, then return true.
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// true || true = true
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// true || false = true
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// false || true = true
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// false || false = false
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System.out.println((10>5) || (20<14));
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System.out.println((10<5) || (20<14) || (10<2) || (1000<999) || (1<0));
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// false, false, false, false, true. Hence, it's true still.
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System.out.println((10<5) || (20<14) || (10<2) || (1000<999) || true);
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// If at the end is true then all is true.
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System.out.println((10<5) || (20<14) || (10<2) || (1000<999) || false);
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// If at the end is all is false then false.
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// NOT(!) - vice-versa
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// true = false
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// false = true
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System.out.println(!(100>99)); // Not true. Therefore, false
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System.out.println(!(100>99) && (2>0));
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// !true AND true = false
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System.out.println(!(20>20) || !(10<=20));
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// !false OR !true = true
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}
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}

‎src/B_04_Ternary_Operator.java‎

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public class B_04_Ternary_Operator {
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public static void main(String[] args) {
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// Ternary Operator ( ?: )
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// condition ? true : false
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int n1 = 10;
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int n2 = 20;
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// if (n2 is greater than n1) then n2 is assigned to variable greaterNum.
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/*
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* So the expression (n2 > n1) ? n2 : n1 means:
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* - If n2 > n1 is true, then use n2.
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* - Otherwise, use n1.
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*/
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int greaterNum = (n2 > n1) ? n2 : n1;
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System.out.println(greaterNum);
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int n3 = 100;
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int n4 = 20;
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int greaterNum2 = (n3 > n4) ? n3 : n4;
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System.out.println(greaterNum2);
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}
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}

‎src/B_05_Increment_Operator.java‎

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public class B_05_Increment_Operator {
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public static void main(String[] args) {
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// Increment Operator (++)
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int a = 10;
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// a++; // post-increment (a = a+1)
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// ++a; // pre-increment (a = 1+a)
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System.out.println(a);
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a++;
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a++;
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System.out.println(a++);
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++a;
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++a;
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System.out.println(++a);
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System.out.println(a++);
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System.out.println(++a);
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// the reason why it's 18 insted of 17 is cause a++ will print out the current value 16 first, only after that it will add up to +1. Hence, the output for ++a would be 17+1 = 18;
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}
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}

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