Science, Tech, Math › Computer Science If-Then and If-Then-Else Conditional Statements in Java What to Do Next Share Flipboard Email Print Thomas Barwick/Stone/ Getty Images Computer Science Java Programming PHP Programming Perl Python Javascript Programming Delphi Programming C & C++ Programming Ruby Programming Visual Basic View More By Paul Leahy Paul Leahy Computer Science Expert M.A., Advanced Information Systems, University of Glasgow Paul Leahy is a computer programmer with over a decade of experience working in the IT industry, as both an in-house and vendor-based developer. Learn about our Editorial Process Updated on July 03, 2019 The if-then and if-then-elseconditional statements let a Java program make simple decisions For example, when making a plan with a friend, you could say "If Mike gets home before 5:00 PM, then we'll go out for an early dinner." When 5:00 PM arrives, the condition (i.e., Mike is home), which determines whether everyone goes out for an early dinner, will either be true or false. It works exactly the same in Java. The if-then Statement Let's say part of a program we're writing needs to calculate if the purchaser of a ticket is eligible for a child's discount. Anyone under the age of 16 gets a 10% discount on the ticket price. We can let our program make this decision by using an if-then if (age < 16) isChild = true; In our program, an integer variable called age holds the age of the ticket purchaser. The condition (i.e., is the ticket purchaser under 16) is placed inside the brackets. If this condition is true, then the statement beneath the if statement is executed -- in this case a boolean variable isChild is set to true The syntax follows the same pattern every time. The if if (condition is true) execute this statement The key thing to remember is the condition must equate to a boolean Often, a Java program needs to execute more than one statement if a condition is true. This is achieved by using a block (i.e., enclosing the statements in curly brackets): if (age < 16){ isChild = true; discount = 10;} This form of the if-then The if-then-else Statement The if-then statement can be extended to have statements that are executed when the condition is false. The if-then-else if (condition) { execute statement(s) if condition is true}else{ execute statement(s) if condition is false} In the ticket program, let's say we need to make sure the discount is equal to 0 if the ticket purchaser is not a child: if (age < 16){ isChild = true; discount = 10;}else{ discount = 0;} The if-then-else statement also allows the nesting of if-then if (age < 16){ isChild = true; discount = 10;}else if (age > 65){ isPensioner = true; discount = 15;}else if (isStudent == true){ discount = 5;} As you can see, the if-then-else statement pattern just repeats itself. If at any time the condition is true , then the relevant statements are executed and any conditions beneath are not tested to see whether they are true or false For example, if the age of the ticket purchaser is 67, then the highlighted statements are executed and the (isStudent == true) There is something worth noting about the (isStudent == true) condition. The condition is written to make it clear that we're testing whether isStudent has a value of true, but because it is a boolean else if (isStudent){ discount = 5;} If this is confusing, the way to think about it is like this -- we know a condition is tested to be true or false. For integer variables like age, we have to write an expression that can be evaluated to true or false (e.g., age == 12, age > 35 However, boolean variables already evaluate to be true or false. We don't need to write an expression to prove it because if (isStudent) is already saying "if isStudent is true..". If you want to test that a boolean variable is false, just use the unary operator!. It inverts a boolean value, therefore if (!isStudent) Cite this Article Format mla apa chicago Your Citation Leahy, Paul. "If-Then and If-Then-Else Conditional Statements in Java." ThoughtCo, Aug. 27, 2020, thoughtco.com/the-if-then-and-if-then-else-statements-2033884. Leahy, Paul. (2020, August 27). If-Then and If-Then-Else Conditional Statements in Java. Retrieved from https://www.thoughtco.com/the-if-then-and-if-then-else-statements-2033884 Leahy, Paul. "If-Then and If-Then-Else Conditional Statements in Java." ThoughtCo. https://www.thoughtco.com/the-if-then-and-if-then-else-statements-2033884 (accessed March 28, 2023). copy citation Featured Video