Conditional statements in Java allow you to execute different blocks of code based on certain conditions. The primary conditional statements are if, else if, and else. Here, we’ll explore these statements with detailed examples to demonstrate their usage in Java.
The if Statement
Executes a block of code if its condition evaluates to true.
Example:
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int number = 10; if (number > 0) { System.out.println("The number is positive."); } // Output: The number is positive. |
The else Statement
Executes a block of code if the condition in the if statement evaluates to false.
Example:
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int number = -10; if (number > 0) { System.out.println("The number is positive."); } else { System.out.println("The number is not positive."); } // Output: The number is not positive. |
The else if Statement
Allows checking of multiple conditions. If if is false, it checks the else if condition. If both are false, else is executed.
Example:
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int number = 0; if (number > 0) { System.out.println("The number is positive."); } else if (number < 0) { System.out.println("The number is negative."); } else { System.out.println("The number is zero."); } // Output: The number is zero. |
Nested if Statements
You can nest if statements within each other for multiple checks.
Example:
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int number = 100; if (number > 0) { if (number < 100) { System.out.println("The number is positive and less than 100."); } else { System.out.println("The number is positive and 100 or more."); } } // Output: The number is positive and 100 or more. |
Using Logical Operators with if Statements
Combine conditions using logical operators.
Example with Logical AND (&&):
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int age = 25; boolean hasLicense = true; if (age >= 18 && hasLicense) { System.out.println("You can drive."); } else { System.out.println("You cannot drive."); } // Output: You can drive. |
Example with Logical OR (||):
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int temperature = 30; if (temperature < 0 || temperature > 35) { System.out.println("Extreme temperature!"); } // No output as the condition is false. |
Example with Logical NOT (!):
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boolean raining = false; if (!raining) { System.out.println("Let's go for a walk!"); } // Output: Let's go for a walk! |
The Ternary Operator
A shorthand for if-else that returns a value.
Example:
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int number = 10; String result = (number > 0) ? "Positive" : "Not Positive"; System.out.println(result); // Output: Positive |
The switch Statement
The switch statement executes one block of code out of many based on the condition. It’s a cleaner alternative to multiple if-else statements for fixed data values.
Example:
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int day = 4; String dayString; switch (day) { case 1: dayString = "Monday"; break; case 2: dayString = "Tuesday"; break; case 3: dayString = "Wednesday"; break; case 4: dayString = "Thursday"; break; case 5: dayString = "Friday"; break; case 6: dayString = "Saturday"; break; case 7: dayString = "Sunday"; break; default: dayString = "Invalid day"; break; } System.out.println("Day of the week: " + dayString); // Output: Day of the week: Thursday |
The switch statement checks the value of day and matches it with a case. If a match is found, it executes the code associated with that case until a break statement is reached, which exits the switch. If no case matches, the default code block is executed.
These examples with detailed explanations and outputs should provide a clearer understanding of how to use conditional statements and the switch statement in Java to control the flow of your programs.