varsopstypes.md(file created)
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| 1 | + | # Java Variables, Operators, and Types | |
| 2 | + | ||
| 3 | + | ## Primitive Data Types | |
| 4 | + | Java has eight primitive data types that store simple values. Here's a comprehensive overview: | |
| 5 | + | ||
| 6 | + | ```java | |
| 7 | + | public class PrimitiveTypes { | |
| 8 | + | public static void main(String[] args) { | |
| 9 | + | // Integer types | |
| 10 | + | byte smallNumber = 127; // 8-bit, range: -128 to 127 | |
| 11 | + | short mediumNumber = 32000; // 16-bit, range: -32,768 to 32,767 | |
| 12 | + | int standardNumber = 2000000000; // 32-bit, range: ~-2B to ~2B | |
| 13 | + | long bigNumber = 9000000000L; // 64-bit, needs 'L' suffix | |
| 14 | + | ||
| 15 | + | // Floating-point types | |
| 16 | + | float decimalNumber = 3.14f; // 32-bit, needs 'f' suffix | |
| 17 | + | double preciseNumber = 3.14159; // 64-bit, default for decimals | |
| 18 | + | ||
| 19 | + | // Character type | |
| 20 | + | char letter = 'A'; // 16-bit Unicode character | |
| 21 | + | ||
| 22 | + | // Boolean type | |
| 23 | + | boolean isActive = true; // true or false | |
| 24 | + | } | |
| 25 | + | } | |
| 26 | + | ``` | |
| 27 | + | ||
| 28 | + | ## Variable Declaration and Initialization | |
| 29 | + | ||
| 30 | + | Variables can be declared and initialized in several ways: | |
| 31 | + | ||
| 32 | + | ```java | |
| 33 | + | public class VariableDeclaration { | |
| 34 | + | public static void main(String[] args) { | |
| 35 | + | // Single declaration | |
| 36 | + | int age; | |
| 37 | + | age = 25; | |
| 38 | + | ||
| 39 | + | // Declaration with initialization | |
| 40 | + | String name = "John"; | |
| 41 | + | ||
| 42 | + | // Multiple declarations | |
| 43 | + | int x, y, z; | |
| 44 | + | x = 1; y = 2; z = 3; | |
| 45 | + | ||
| 46 | + | // Multiple declarations with initialization | |
| 47 | + | double height = 5.9, weight = 68.5; | |
| 48 | + | ||
| 49 | + | // Constants (final variables) | |
| 50 | + | final double PI = 3.14159; | |
| 51 | + | final int MAX_USERS = 100; | |
| 52 | + | } | |
| 53 | + | } | |
| 54 | + | ``` | |
| 55 | + | ||
| 56 | + | ## Type Conversion and Casting | |
| 57 | + | ||
| 58 | + | Java supports both implicit (automatic) and explicit (manual) type conversion: | |
| 59 | + | ||
| 60 | + | ```java | |
| 61 | + | public class TypeConversion { | |
| 62 | + | public static void main(String[] args) { | |
| 63 | + | // Implicit conversion (widening) | |
| 64 | + | int smallNum = 100; | |
| 65 | + | long bigNum = smallNum; // int to long | |
| 66 | + | float floatNum = bigNum; // long to float | |
| 67 | + | ||
| 68 | + | // Explicit conversion (narrowing) | |
| 69 | + | double price = 99.99; | |
| 70 | + | int roundedPrice = (int) price; // Loses decimal part | |
| 71 | + | ||
| 72 | + | // String conversion | |
| 73 | + | String strNumber = "123"; | |
| 74 | + | int parsedInt = Integer.parseInt(strNumber); | |
| 75 | + | double parsedDouble = Double.parseDouble("123.45"); | |
| 76 | + | ||
| 77 | + | // Converting numbers to String | |
| 78 | + | String strValue = String.valueOf(parsedInt); | |
| 79 | + | String anotherStr = Integer.toString(parsedInt); | |
| 80 | + | } | |
| 81 | + | } | |
| 82 | + | ``` | |
| 83 | + | ||
| 84 | + | ## Operators | |
| 85 | + | ||
| 86 | + | ### Arithmetic Operators | |
| 87 | + | ```java | |
| 88 | + | public class ArithmeticOperators { | |
| 89 | + | public static void main(String[] args) { | |
| 90 | + | int a = 10, b = 3; | |
| 91 | + | ||
| 92 | + | System.out.println("Addition: " + (a + b)); // 13 | |
| 93 | + | System.out.println("Subtraction: " + (a - b)); // 7 | |
| 94 | + | System.out.println("Multiplication: " + (a * b)); // 30 | |
| 95 | + | System.out.println("Division: " + (a / b)); // 3 | |
| 96 | + | System.out.println("Modulus: " + (a % b)); // 1 | |
| 97 | + | ||
| 98 | + | // Increment and decrement | |
| 99 | + | int count = 5; | |
| 100 | + | System.out.println(count++); // Prints 5, then increments | |
| 101 | + | System.out.println(++count); // Increments, then prints 7 | |
| 102 | + | } | |
| 103 | + | } | |
| 104 | + | ``` | |
| 105 | + | ||
| 106 | + | ### Comparison Operators | |
| 107 | + | ```java | |
| 108 | + | public class ComparisonOperators { | |
| 109 | + | public static void main(String[] args) { | |
| 110 | + | int x = 5, y = 8; | |
| 111 | + | ||
| 112 | + | System.out.println(x == y); // Equal to: false | |
| 113 | + | System.out.println(x != y); // Not equal to: true | |
| 114 | + | System.out.println(x > y); // Greater than: false | |
| 115 | + | System.out.println(x < y); // Less than: true | |
| 116 | + | System.out.println(x >= y); // Greater than or equal: false | |
| 117 | + | System.out.println(x <= y); // Less than or equal: true | |
| 118 | + | } | |
| 119 | + | } | |
| 120 | + | ``` | |
| 121 | + | ||
| 122 | + | ### Logical Operators | |
| 123 | + | ```java | |
| 124 | + | public class LogicalOperators { | |
| 125 | + | public static void main(String[] args) { | |
| 126 | + | boolean isValid = true; | |
| 127 | + | boolean isActive = false; | |
| 128 | + | ||
| 129 | + | System.out.println(isValid && isActive); // AND: false | |
| 130 | + | System.out.println(isValid || isActive); // OR: true | |
| 131 | + | System.out.println(!isValid); // NOT: false | |
| 132 | + | ||
| 133 | + | // Short-circuit evaluation | |
| 134 | + | int num = 10; | |
| 135 | + | if (num > 0 && num++ < 20) { | |
| 136 | + | System.out.println(num); // Prints 11 | |
| 137 | + | } | |
| 138 | + | } | |
| 139 | + | } | |
| 140 | + | ``` | |
| 141 | + | ||
| 142 | + | ### Assignment Operators | |
| 143 | + | ```java | |
| 144 | + | public class AssignmentOperators { | |
| 145 | + | public static void main(String[] args) { | |
| 146 | + | int value = 10; | |
| 147 | + | ||
| 148 | + | value += 5; // value = value + 5 | |
| 149 | + | value -= 3; // value = value - 3 | |
| 150 | + | value *= 2; // value = value * 2 | |
| 151 | + | value /= 4; // value = value / 4 | |
| 152 | + | value %= 3; // value = value % 3 | |
| 153 | + | ||
| 154 | + | // Bitwise assignment operators | |
| 155 | + | int flags = 5; | |
| 156 | + | flags &= 3; // Bitwise AND assignment | |
| 157 | + | flags |= 4; // Bitwise OR assignment | |
| 158 | + | flags ^= 1; // Bitwise XOR assignment | |
| 159 | + | } | |
| 160 | + | } | |
| 161 | + | ``` | |
| 162 | + | ||
| 163 | + | Remember these key points about Java variables and operators: | |
| 164 | + | - Variables must be declared before use | |
| 165 | + | - Java is strongly typed, meaning type checking happens at compile time | |
| 166 | + | - The type of a variable determines what operations can be performed on it | |
| 167 | + | - Implicit type conversion only works when going from a smaller to a larger data type | |
| 168 | + | - Explicit type conversion (casting) is required when going from a larger to a smaller data type | |
| 169 | + | - Operators follow a specific precedence order when evaluating expressions | |
| 170 | + | - Short-circuit evaluation in logical operators can improve performance | |
| 171 | + | ||
| 172 | + | Practice with these examples to better understand how variables, types, and operators work together in Java programs. | |
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