All Decision Making Statements In Java Explained (+Code Examples)

Decision-making statements in Java are constructs that allow us to control the flow of execution based on specific conditions. These statements enable programs to "decide" which block of code to execute depending on whether a condition evaluates to true or false. Essentially, they bring logic into our code, helping it respond dynamically to varying inputs or states.

In this article, we'll explore the core decision-making statements in Java, including if, if-else, else-if, switch, and more. We’ll dive into their syntax, use cases, and examples to understand how they work and when to use each of them effectively.

What Is Decision Making Statement In Java?

In Java programming, decision-making statements allow us to execute certain blocks of code based on specific conditions. They are used to control the flow of execution in a program, making it possible to decide which action to take based on whether a condition is true or false. These statements help in making decisions during runtime.

Here are the different types of decision-making statements in Java:

• If Statement: The if statement evaluates a condition and executes the block of code inside it only if the condition is true.
• If-else Statement: The if-else statement provides two options: one for when the condition is true and another for when it is false.
• Else-if Ladder: The else-if ladder is used when we have multiple conditions to check. It allows us to check for more than two conditions.
• Switch Statement: The switch statement is used when we have a variable that can take one of several values, and we want to execute different code depending on its value.
• Ternary Operator (?:): The ternary operator is a shorthand for the if-else statement. It evaluates a condition and returns one of two values based on whether the condition is true or false.

We will now discuss each of these statements in detail in the sections ahead.

If Statement In Java

The if statement in Java is a fundamental control structure that allows us to execute a block of code only when a specified condition is true. It is used for decision-making and helps in controlling the flow of a program based on conditions.

Syntax Of The If Statement In Java

if (condition) {
    // code to be executed if the condition is true
}

Here: 

• if: The keyword that initiates the conditional check.
• Condition: A boolean expression that is evaluated. If the condition is true, the block of code inside the if statement is executed.
• Code Block: A set of one or more statements that will execute if the condition evaluates to true. The code block is enclosed in curly braces {}.

Let’s look at an example to understand how the if statement works in Java:

Code Example: 

Output (set code file name as IfExample.java): 

The number is greater than 5

Explanation: 

In the above code example-

1. We start by defining a class called IfExample. This class contains the main() method, which serves as the entry point for the program.
2. Inside the main method, we declare an integer variable named number and initialize it with a value of 10. This variable will be used in the conditional check.
3. We then use an if statement to check if the value of number is greater than 5. The condition we are testing is number > 5.
4. Since number is 10, which is indeed greater than 5, the condition evaluates to true.
5. When the condition is true, the code inside the if block gets executed. This block contains the System.out.println() statement, which prints the message "The number is greater than 5" to the console.
6. If the value of number were less than or equal to 5, the code inside the if block would not execute, and nothing would be printed.

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If-Else Statement In Java

The if-else statement is an extension of the if statement. It allows us to execute one block of code if a condition is true, and another block of code if the condition is false. This provides a way to handle two possible scenarios and control the flow of the program based on the condition.

Syntax Of The If-Else Statement In Java

if (condition) {
    // code to be executed if the condition is true
} else {
    // code to be executed if the condition is false
}

Here: 

• if: The keyword that starts the condition evaluation.
• Condition: A boolean expression that evaluates to true or false.
• else: The keyword that begins the alternative block of code, which runs if the condition is false.

Here’s an example using the if-else statement in Java-

Code Example:

Output (set code file name as IfElseExample.java): 

The number is not greater than 5

Explanation: 

In the above code example-

1. We define a class called IfElseExample, and within this class, we have the main() method, which is the starting point of our program.
2. Inside the main method, we declare an integer variable named number and initialize it with the value 3. This variable will be used in the conditional check.
3. Next, we use an if-else statement to evaluate whether the value of number is greater than 5. The condition being tested is number > 5.
4. Since the value of number is 3, which is less than 5, the condition evaluates to false.
5. As the condition is false, the program skips over the code inside the if block and instead executes the code in the else block.
6. The else block contains a System.out.println() statement that prints "The number is not greater than 5" to the console.
7. If number had been greater than 5, the program would have printed "The number is greater than 5" instead.

Else-If Ladder In Java

The else-if ladder is an extension of the if-else statement. It allows us to check multiple conditions in sequence. If the first condition is false, the program evaluates the next condition, and so on. This is useful when we have more than two possible outcomes and need to execute different blocks of code for each case.

Syntax Of The Else-If Ladder In Java

if (condition1) {
    // code to be executed if condition1 is true
} else if (condition2) {
    // code to be executed if condition2 is true
} else if (condition3) {
    // code to be executed if condition3 is true
} else {
    // code to be executed if none of the conditions are true
}

Here: 

• if: Starts the evaluation of the first condition.
• else if: Checks additional conditions if the previous conditions were false.
• Condition: Each condition is a boolean expression that is checked sequentially.
• else: The default block that executes if none of the conditions evaluate to true.

Given below is an example demonstrating the else-if ladder in Java programming-

Code Example: 

Output (set code file name as ElseIfExample.java): 

The number is greater than 10 but less than or equal to 20

Explanation: 

In the above code example-

1. We define a class called ElseIfExample, and within it, we have the main() method, which is where the program starts execution.
2. Inside the main method, we declare an integer variable number and initialize it with the value 15. This variable will be used in a series of conditional checks.
3. We then use an if-else if-else ladder to check different conditions based on the value of number.
4. The first condition checks if number is greater than 20 (number > 20). Since the value of number is 15, which is not greater than 20, this condition is false, so the program moves to the next condition.
5. The second condition checks if number is greater than 10 (number > 10). Since 15 is indeed greater than 10, this condition evaluates to true.
6. Because this condition is true, the code inside the corresponding block gets executed, which prints "The number is greater than 10 but less than or equal to 20" to the console.
7. The remaining else if and else blocks are skipped since the condition in the second else if was true.
8. If none of the conditions had been true, the else block would have been executed, printing "The number is 5 or less."

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Switch Statement In Java

The switch statement in Java is a control structure that allows us to choose one of many code blocks to execute based on the value of a variable or expression. It's an alternative to using multiple if-else statements when there are multiple possible outcomes for a given condition. This makes the code cleaner and more readable when dealing with multiple conditions.

Syntax Of Switch Statement In Java

switch (expression) {
    case value1:
        // code to be executed if expression == value1
        break;
    case value2:
        // code to be executed if expression == value2
        break;
    case value3:
        // code to be executed if expression == value3
        break;
    default:
        // code to be executed if no cases match
}

Here: 

• switch: The keyword that begins the switch block.
• Expression: The value that is evaluated. It can be of types like int, char, String, etc.
• case: Defines possible values that the expression is compared against.
• break: The statement that exits the switch block once a match is found.
• default: A fallback block of code that is executed if none of the cases match.

Here’s an example demonstrating the use of the switch statement in Java-

Code Example: 

Output (set code file name as SwitchExample.java): 

Wednesday

Explanation: 

In the above code example-

1. We define a class called SwitchExample, and within it, we have the main() method, which serves as the entry point for the program.
2. Inside the main method, we declare an integer variable named day and initialize it with the value 3. This variable represents the day of the week, with 1 for Monday, 2 for Tuesday, and so on.
3. We then use a switch statement to check the value of day and print the corresponding day of the week.
4. The switch statement evaluates the value of day and compares it with the values in each case block.
5. Since the value of day is 3, the program matches the case 3 block. This block contains the statement System.out.println("Wednesday");, so the program prints "Wednesday" to the console.
6. The break statement in each case block ensures that once a match is found and the corresponding action is executed, the program exits the switch statement, preventing the execution of subsequent cases.
7. If the value of day did not match any of the specified cases (for example, if it were a number outside the range of 1 to 7), the default block would execute, printing "Invalid day."

Ternary/Conditional Operator (?:) In Java

The ternary operator (also known as the conditional operator) is a shorthand for the if-else statement. It provides a concise way to evaluate a condition and choose between two expressions based on whether the condition is true or false. The ternary operator is often used for simple conditions and assignments.

Syntax Of Ternary Operator In Java

condition ? expressionIfTrue : expressionIfFalse;

Here:

• Condition: A boolean expression that is evaluated.
• ?: The operator that separates the condition from the expressions.
• Expression if true: The code or value that will be executed/returned if the condition is true.
• Expression if false: The code or value that will be executed/returned if the condition is false.

Let’s look at a code example to understand the working of ternary operator in Java-

Code Example: 

Output (set code file name as TernaryOperatorExample.java): 

The number is: Even

Explanation: 

In the above code example-

1. We define a class called TernaryOperatorExample, and within this class, we have the main() method, which is the entry point of the program.
2. Inside the main method, we declare an integer variable number and initialize it with the value 8. This variable will be checked to determine if it is even or odd.
3. We then use the ternary operator to check whether number is even or odd. The ternary operator has the following structure: condition ? valueIfTrue : valueIfFalse.
4. In this case, the condition is number % 2 == 0, which checks if the number is divisible by 2 (i.e., if it is even).
5. Since the value of number is 8, which is divisible by 2, the condition evaluates to true. As a result, the value "Even" is assigned to the result variable.
6. If number had been an odd number (e.g., 7), the condition would have been false, and the value "Odd" would have been assigned to result.
7. Finally, we use System.out.println() to print the message "The number is: Even" to the console, as result contains the string "Even."

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Best Practices For Writing Decision Making Statements In Java

When writing decision-making statements in Java, it's important to focus on readability, maintainability, and efficiency. Here are some best practices that can help you write clean, effective decision-making logic:

• Keep Conditions Simple: Avoid complex conditions with multiple logical operators (&&, ||). If needed, break them down into simpler conditions or use intermediate variables to improve readability. For Example-

boolean isWeekend = day == 6 || day == 7;
if (isWeekend) {
    // Do something
}

• Avoid Deeply Nested Statements: Excessive nesting can make code hard to read and maintain. Use early returns (in methods) or simplify logic with functions that handle complex conditions separately. For Example-

if (condition1) {
    if (condition2) {
        // Do something
    }
}

• Use switch for Multiple Discrete Conditions: For checking the same variable against multiple possible values, switch is often more readable and efficient than an if-else ladder. For Example-

switch (day) {
    case 1: System.out.println("Monday"); break;
    case 2: System.out.println("Tuesday"); break;
    case 3: System.out.println("Wednesday"); break;
    default: System.out.println("Invalid day");
}

• Use default in switch Statements: Always include a default case in a switch statement to handle unexpected values, improving code robustness and making the logic easier to follow. For Example-

switch (day) {
    case 1: // Monday
    case 2: // Tuesday
    default: // Handle invalid days
}

• Use Meaningful Variable Names: Ensure that the variables used in the conditions have meaningful names that clearly describe their role. This enhances readability. For Example-

int age = 25;
if (age >= 18) { // instead of "x" or "num"
    System.out.println("Adult");
}

• Be Careful with Floating Point Comparisons: Avoid direct comparison of floating-point numbers (float, double) due to precision issues. Instead, use a tolerance value to compare them. For Example-

double tolerance = 0.0001;
if (Math.abs(a - b) < tolerance) {
    // Consider a and b equal
}

• Avoid Complex Boolean Expressions: When dealing with complex boolean conditions, use descriptive variables for readability. For Example-

boolean isEligibleForDiscount = age > 18 && age < 60;
if (isEligibleForDiscount) {
    // Apply discount
}

• Handle All Possible Conditions: Make sure that all possible conditions are handled. For example, in a switch statement, always include a default case to handle unexpected inputs.
• Document Complex Conditions: If a condition is non-trivial, consider adding comments to explain why it’s necessary. This helps future maintainers understand the reasoning behind the logic. For Example-

// Check if the user is eligible for a special offer
if (userAge > 18 && hasValidSubscription) {
    // Process the offer
}

• Optimize for Performance: In performance-critical applications, evaluate conditions that are likely to be true first to reduce the number of evaluations. For Example-

if (isValid && isAvailable) {
    // Proceed with operations
}

Conclusion

In Java programming language, decision-making statements are essential for directing the flow of execution based on specific conditions. Whether you're using an if-else statement for simple choices, an else-if ladder for multiple conditions, a switch statement for discrete values, or the ternary operator for compact expressions, each decision-making tool has its unique use case. 

By following best practices such as keeping conditions simple, choosing the most appropriate statement, avoiding deep nesting, and ensuring readability, you can write clean, efficient, and maintainable code. Proper use of these structures ensures your Java applications are not only logical but also clear and robust, making them easier to maintain and extend in the future.

Frequently Asked Questions

Q. What is the difference between if and if-else statements in Java?

The if statement allows you to execute a block of code if a condition is true. If the condition is false, the program simply skips the block. On the other hand, the if-else statement allows you to specify an alternative block of code to execute when the condition is false. This provides a two-way choice: one block of code executes if the condition is true, and another executes if it's false.

Q. What is an else-if ladder, and when should it be used?

An else-if ladder is used when there are multiple conditions to evaluate sequentially. If the first condition is false, the program evaluates the next condition in the ladder, and so on, until a true condition is found or the else block (if present) is executed as the default.

It should be used when you have more than two conditions to check, and you need to execute a different block of code depending on which condition is true.

Q. When should I use the switch statement over if-else in Java?

A switch statement is most effective when you need to compare the same variable or expression against multiple possible constant values. It is more efficient and readable compared to a chain of if-else statements when there are many potential conditions to check. The switch is also easier to maintain, as it consolidates the multiple conditions into one structure.

Q. What are the advantages of using the ternary operator in Java?

The ternary operator provides a concise, single-line alternative to if-else statements, making your code shorter and potentially more readable for simple conditions. It is especially useful when assigning values based on a condition or performing quick decisions in expressions. However, it should be used sparingly, as overuse can lead to decreased readability in more complex conditions.

Q. Can I use multiple conditions in an if statement in Java?

Yes, you can use multiple conditions in an if statement by combining them with logical operators such as && (AND) and || (OR). This allows you to check for more complex conditions. For Example-

if (age > 18 && hasLicense) {
    System.out.println("Eligible to drive");
}

Q. What are the limitations of using the switch statement in Java?

While the switch statement is great for handling multiple discrete values, it does have some limitations:

• It can only evaluate expressions that are of type byte, short, char, int, String, and their corresponding wrapper classes. You cannot use objects or boolean values.
• A switch statement evaluates values exactly as they are, so it can’t handle ranges or conditions like if statements can.
• It is limited to comparing one expression against multiple cases, and if you have conditions that require different variables to be compared, if-else or else-if might be more appropriate.

Q. How can I improve the readability of complex decision-making logic?

To improve readability:

• Break complex conditions into smaller, more descriptive variables.
• Avoid deeply nested if statements by using early returns in methods.
• Use comments to explain non-obvious conditions.
• Prefer switch when evaluating the same variable against multiple values.
• Maintain consistent formatting and indentation to make the decision-making logic clear.
• Refactor lengthy if-else chains into methods or helper functions if they involve complex logic.

With this, we come to an end of our discussion on the decision-making statements in Java. Here are a few other topics that you might be interested in reading: 

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