Java Switch Statement: Everything You Need to Know

As you are learning to program in Java, there are quite a few logic statements you can use to control the flow of execution. Obviously, if-then statements are probably the simplest and most widely used, but there are quite a few other statements that are extremely powerful once you understand how to use them. One of these statements is known as the switch statement and it is Java’s multi-way branch statement.

Using the switch statement allows you to dispatch execution of your code to different parts of the program based on the value of a given expression. You can learn more about using switch statements in your programs in Learn Java from Scratch.

To help you understand the construction of a switch statement better, take a look at the following example which demonstrates the basics of the Java switch statement:

switch (expression) {

case value1:

//statement sequence

break;

case value2:

//statement sequence

break;

case valueN:

//statement sequence

break;

default:

//default statement sequence

}

The expression must be a byte, short, int, or char with each of the value specified in the case statements being compatible with the expression. String can also be used as a case expression as long as the case statements are compatible with the expression. For instance, you cannot add a number to a string value.

How Switch Statements Work

When the flow of execution in your program reaches the switch statement, the value of the expression is compared with each of the literal values in the case statements. If a match is found, the code sequence following that case statement is executed. If none of the constants match the value of the expression, the default statement is executed. The default statement is optional, however, and if no default is present and no case matches the expression, then no further action is taken and the flow of execution moves past the switch statement into the next part of the program.

The break statement within the switch terminates a statement sequence. When your program encounters a break statement, execution redirects to the first line of code following the entire switch statement. It may be easier to understand if you look at the following Java code example that uses a switch statement to determine the “grade” of an employee and the associated bonus they receive.

Notice that in this example, the grade is hardcoded with the statement char Grade = ‘B’;. Typically, the expression will contain variables that are dependent on other parts of the program as a hard coded variable negates the purpose of using the switch statement in the first place.

public class SwitchCaseDemo {

        public static void main(String[] args) {

                    char Grade =’B’;

                    switch (Grade){

                    case ‘A’:

                                System.out.println(“You are a Grade A Employee: Bonus= “+ 2000);

                                break;

                    case ‘B’:

                                System.out.println(“You are a Grade B Employee: Bonus= “+ 1000);

                                break;

                    case ‘C’:

                                System.out.println(“You are a Grade C Employee: Bonus= “+ 500);

                                break;

                    default:

                                System.out.println(“You are a Default Employee: Bonus= “+ 100);

                                break;

                    }                   

        }

}

In this example, the output of the program would be “You are a Grade B Employee: Bonus = 1000.” Of course, this is a simplified example but it is a functional switch statement that could easily be adopted for more practical use in your own Java applications.

Nested Switch Statements

The switch statement can also be used as part of the statement sequence of an outer switch. This is called a nested switch and is exactly the same idea as a nested if-then statement. Creating nested switch statements is slightly more complex, but the good news is that there are no conflicts between the case constants in the inner switch and those in the outer switch because each switch statement defines its own block.

You may find yourself using nested switch statements in many applications as they require less work than nested if statements and do not have some of the compatibility issues that can be inherent to complex nested if-then statements.

The Ultimate Java Tutorial explains how to use nested switch statements effectively.

Important Facts about Switch Statements

There are a couple of things you should realize when you use switch statements in your Java applications. For one, the switch can only check for equality. This means that no other relational operators (such as greater than or less than) can be used within a case. Case constants are always evaluated from the top down. This means that the first case matching the switch expression is the execution entry point. If no break statement is used, all cases after the entry point will be executed.

Within the same switch statement, no two case constants can have identical values. Remember that this is not true if you are using nested switch statements.

Although it is a best practice to include your default case at the end of your switch statement, technically it can be located anywhere within the switch statement. This really comes down to your own personal preference and what makes sense to you while creating your Java application. Java – Make it Your Cup of Coffee covers switch statements and how to use default cases.

Learning how to effectively use Java switch statements can drastically increase the quality of your programs. Not only can it decrease the amount of code required, but it also is less processor intensive when you start working on complex desktop applications with thousands of lines of code.

Remember that you can use switch statements alone or you can nest them within each other for very large, complex statements that accomplish multiple tasks simultaneously.

Using the example in this article, play around with switch statements to learn more about how they work. Remove the break statement and see how that affects operation. Although break statements are typically required, there may be situations where you want all code to be executed after the entry point and you would intentionally leave break statements out of those particular cases. You can learn more about the appropriate use of the break statement in the Introduction to Java Training Course.

Once you have mastered switch statements, you will be well on your way to becoming a professional Java programmer that is capable of creating efficient and powerful applications for the desktop and the Web.