Switch Statement in Java

Some Important Rules for Switch Statements

Here are some important rules for Java switch statements:

• The switch statement's expression needs to be of a type that can be compared to integers. This comprises the class String, the enum types, and the primitive types byte, short, char, and int.
   
• The case labels must be literals or constants of the same type as the switch statement's expression.
   
• Although using the break statement to exit the switch statement once the desired case has been executed is optional, it is a recommended strategy. If the break statement is not used, the next case label will be executed even if the expression's value does not match.
   
• The default case is not required. The switch statement will automatically go on to the following statement if neither the default case nor a case label that matches the value of the expression are present.

How does the Switch Statement Work?

When a switch statement is executed the expression is evaluated then compared to each of the case labels. 

• If a matching case is found, then the corresponding code block is executed. 
   
• If there is no matching case, then the code in the default block is executed (if it is defined). 
   

The break statement is used to exit the switch block.

Flowchart of Switch-Case Statement

Break in Switch-Case Statement

In Java, the switch statement provides a way to execute different blocks of code based on the value of a variable or expression. The break statement within a switch case is crucial as it terminates the execution of the switch block. Here's an explanation with an example:

 

Output

Day 3 is Wednesday

 

Explanation:

1. Switch Statement: The switch statement evaluates the day variable.
2. Case Statements: Each case label checks if day matches a specific value.
3. Break Statement: The break; statement terminates the switch block after each case is executed. Without break;, execution would fall through to subsequent cases.
4. Default Case: If day does not match any case, the default case assigns dayName to "Invalid day".
5. Output: In this example, since day is 3, the output will be: Day 3 is Wednesday.

Java Nested Switch Statement

A nested switch case is a switch statement that is contained within another switch statement. 

In other words, it is a switch statement that is used as one of the statements inside another switch statement.

Nested Switch Case Syntax

The syntax for a nested switch case is very similar to that of a regular switch case, with the addition of an inner switch statement inside one of the case blocks of the outer switch statement.

switch (outer) {

  case outerCase1:
    // do something
    
    switch (inner) {
    
      case innerCase1:
        // do something
        break;
        
      case innerCase2:
        // do something
        break;
        
      default:
        // do something
        break;
        
    }
    // do something
    break;
    
  case outerCase2:
    // do something
    
  default:
    // do something
    break;
}

In this syntax, outer is the variable that is being evaluated in the outer switch statement, and outerCase1, outerCase2, etc., are the different cases that the switch statement can match.

Inside one of the case blocks of the outer switch statement, there is an inner switch statement that evaluates the value of inner. innerCase1, innerCase2, etc., are the different cases that the inner switch statement can match.

Each case block in both the outer and inner switch statements can contain statements to execute when that case is matched. Both switch statements end with a break statement to exit the switch block.

Let us take an example: 

In this example, we have an outer switch statement that evaluates the value of outerVar. If outerVar is equal to 2, then we have a nested switch statement that evaluates the value of innerVar.

Code in Java

Output

Inner-case 1

Explanation: 

If innerVar is equal to 1, then the inner switch statement matches the first case and prints "Inner case 1". 

Otherwise, if innerVar is equal to 2, the inner switch statement matches the second case and prints "Inner case 2". 

If innerVar is not 1 or 2, the inner switch statement matches the default case and prints "Invalid inner case".

If outerVar is not 2, the outer switch statement checks the other cases and prints out the corresponding messages.

Java Switch Statement with String

We can take different actions based on the values of strings by using the Java switch statement with a string. The following describes how to use a switch statement with strings:

Output

It's Tuesday!

Java Enum in Switch Statement

When working with a set of fixed constant values in Java, we can utilise an enum type in a switch statement to produce simpler and maintainable code. An example of how to utilise an enum in a switch statement is given below:

Output:

Today is a fun Saturday.

Java Wrapper in Switch Statement

Switch statements may be used with Java wrapper classes. Byte, Short, Character, and Integer are the respective wrapper classes for the primitive types Byte, Short, Character, and Integer. String serves as the String class's wrapper.

As an example, the switch statement in the following code, which makes use of the wrapper class Integer, is valid:

Output:

Wednesday

Default Statement in Java Switch Case

In Java's switch statement, the default case serves as a catch-all option that executes when none of the preceding case labels match the evaluated expression. Here's an explanation with an example:

Output:

Day 7 is Weekend

 

Explanation:

1. Switch Statement: The switch statement evaluates the day variable.
2. Case Statements: Each case label checks if day matches a specific value from 1 to 5.
3. Default Case: If day does not match any of the specified case labels (1 to 5), the default case is executed.
4. Output: In this example, since day is 7 (which does not match any case), the output will be: Day 7 is Weekend.

Case Label Variations in Java Switch Case

In Java, switch case labels can vary in terms of the types they support and how they are evaluated. Here are some variations:

1. Integer Case Labels:

int number = 2;
switch (number) {
    case 1:
        System.out.println("One");
        break;
    case 2:
        System.out.println("Two");
        break;
    // More cases
}

 

2. Character Case Labels:

char grade = 'B';
switch (grade) {
    case 'A':
        System.out.println("Excellent");
        break;
    case 'B':
        System.out.println("Good");
        break;
    // More cases
}

 

3. Enum Case Labels:

enum Day {
    MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY
}

Day today = Day.WEDNESDAY;
switch (today) {
    case MONDAY:
        System.out.println("Start of the week.");
        break;
    case WEDNESDAY:
        System.out.println("Middle of the week.");
        break;
    // More cases
}

Use of Switch Case in Java

Cleaner Code: When compared to employing a number of nested if-else statements for various situations, they make the code more legible and maintainable.

Multiple Branching: Switch-case statements are used when a single variable or expression must be tested under several different situations.

Value-Based Branching: You can utilise Enums and integral types (int, char, byte, and short) as the controlling expression in a switch-case statement.

Effective: When dealing with a lot of conditions, switch-case statements are frequently more effective than utilising many if-else statements.

Advantages of Java Switch over If-Else

Below are some of the advantages of switch over if-else: 

• Simplifies code - Using a switch statement can be simpler and more concise than using multiple if-else statements to test the same variable or expression against different values.
   
• Readability - Switch statements are often easier to read and understand than multiple if-else statements, especially when testing for a large number of values.
   
• Performance - The use of switch statements can often lead to faster execution times than equivalent if-else statements, especially when the number of values being tested is large.
   
• Error-prone - Switch statements are less error-prone than using multiple if-else statements because each case must have a unique value, and the default case can catch any unexpected values.
   
• Better control - Switch statements provide better control flow than if-else statements because the break statement is used to exit the switch statement after the matching case is executed.

Frequently Asked Questions

What is a switch case in Java?

A control flow structure known as a switch-case statement is used in Java to make decisions based on the value of an expression. Based on the expression's value, you can choose from a variety of code blocks to execute.

How to use switch and case in Java?

In Java, you must specify the expression to be evaluated within the switch statement in order to use a switch-case statement. Each case label reflects one of the expression's potential values. The matching code block is performed when an expression matches a case value.

Do you need a break in switch case Java?

Yes, break; is necessary to terminate each case block in a switch statement to prevent fall-through to subsequent cases.

How to write a switch case?

Write a switch statement with case labels for each condition, followed by code blocks and break; statements to separate each case's execution.

How to use switch case in Java for char?

Use char values as case labels in a switch statement to execute specific code blocks based on the evaluated character value.

Why is switch case used?

Switch case is used to efficiently execute different blocks of code based on the value of a variable or expression in Java programming.

Conclusion

The switch case java statement is an important concept in Java programming that allows you to execute different blocks of code based on the value of a given expression or variable.

By using a switch statement, you can simplify your code, improve its readability, and optimize its performance. With the right implementation, the switch statement can help you write better and more efficient code in Java.

Also read - Jump statement in java

To know more about decision-making statements, refer to this article. 

Happy Learning!