1. Lesson: Language Basics
  2. Variables
    1. Naming
    2. Primitive Data Types
    3. Default Values
    4. Literals
    5. Using Underscore Characters in Numeric Literals
    6. Arrays
    7. Declaring a Variable to Refer to an Array
    8. Creating, Initializing, and Accessing an Array
    9. Copying Arrays
    10. Summary of Variables
    11. Questions and Exercises: Variables
  3. Expressions, Statements, and Blocks
    1. Expressions
    2. Statements
    3. Blocks
    4. Questions and Exercises: Expressions, Statements, and Blocks
  4. Control Flow Statements
    1. The if-then Statement
    2. The if-then-else Statement
    3. The switch Statement
    4. Using Strings in switch Statements
    5. The while and do-while Statements
    6. The for Statement
    7. The break Statement
    8. The continue Statement
    9. The return Statement
    10. Summary of Control Flow Statements
    11. Questions and Exercises: Control Flow Statements
  5. Lesson: Classes and Objects
    1. Classes
    2. Declaring Classes
    3. Declaring Member Variables
    4. Access Modifiers
    5. Types
    6. Variable Names
    7. Defining Methods
    8. Naming a Method
    9. Overloading Methods
    10. Providing Constructors for Your Classes
    11. Passing Information to a Method or a Constructor
    12. Parameter Types
    13. Arbitrary Number of Arguments
    14. Parameter Names
    15. Passing Primitive Data Type Arguments
    16. Passing Reference Data Type Arguments
    17. Objects
    18. Creating Objects
    19. Declaring a Variable to Refer to an Object
    20. Instantiating a Class
    21. Initializing an Object
    22. Using Objects
    23. Referencing an Object's Fields
    24. Calling an Object's Methods
    25. The Garbage Collector
    26. More on Classes
    27. Returning a Value from a Method
    28. Returning a Class or Interface
    29. Using the this Keyword
    30. Using this with a Field
    31. Using this with a Constructor
    32. Controlling Access to Members of a Class
    33. Understanding Instance and Class Members
    34. Class Variables
    35. Class Methods
    36. Constants
    37. The Bicycle Class
    38. Initializing Fields
    39. Static Initialization Blocks
    40. Initializing Instance Members
    41. Summary of Creating and Using Classes and Objects
    42. Questions and Exercises: Classes
    43. Questions and Exercises: Objects
  6. Nested Classes
    1. Why Use Nested Classes?
    2. Static Nested Classes
    3. Inner Classes
    4. Inner Class Example
    5. Local and Anonymous Inner Classes
    6. Modifiers
    7. Summary of Nested Classes
    8. Questions and Exercises: Nested Classes
  7. Enum Types
    1. Questions and Exercises: Enum Types
  8. Annotations
    1. Documentation
    2. Annotations Used by the Compiler
    3. Annotation Processing
    4. Questions and Exercises: Annotations
  9. Lesson: Interfaces and Inheritance
    1. Interfaces
    2. Interfaces in Java
    3. Interfaces as APIs
    4. Interfaces and Multiple Inheritance
    5. Defining an Interface
    6. The Interface Body
    7. Implementing an Interface
    8. A Sample Interface, Relatable
    9. Implementing the Relatable Interface

4.3.The switch Statement #

Unlike if-then and if-then-else statements, the switch statement can have a number of possible execution paths. A switch works with the byte, short, char, and int primitive data types. It also works with enumerated types (discussed in Enum Types), the String class, and a few special classes that wrap certain primitive types: Character, Byte, Short, and Integer (discussed in Numbers and Strings).
The following code example, SwitchDemo, declares an int named month whose value represents a month. The code displays the name of the month, based on the value of month, using the switch statement.

public class SwitchDemo {	
    public static void main(String[] args) 
        int month = 8;
        String monthString;
        switch (month) {
            case 1:  monthString = "January";
            case 2:  monthString = "February";
            case 3:  monthString = "March";
            case 4:  monthString = "April";         
            case 5:  monthString = "May";
            case 6:  monthString = "June";
            case 7:  monthString = "July";
            case 8:  monthString = "August";   
            case 9:  monthString = "September";
            case 10: monthString = "October";
            case 11: monthString = "November";
            case 12: monthString = "December"; 
            default: monthString = "Invalid month"; 

In this case, August is printed to standard output.
The body of a switch statement is known as a switch block. A statement in the switch block can be labeled with one or more case or default labels. The switch statement evaluates its expression, then executes all statements that follow the matching case label.
You could also display the name of the month with if-then-else statements:

int month = 8;
if (month == 1) {
} else if (month == 2) {

. . . // and so on
Deciding whether to use if-then-else statements or a switch statement is based on readability and the expression that the statement is testing. An if-then-else statement can test expressions based on ranges of values or conditions, whereas a switch statement tests expressions based only on a single integer, enumerated value, or String object.
Another point of interest is the break statement. Each break statement terminates the enclosing switch statement. Control flow continues with the first statement following the switch block. The break statements are necessary because without them, statements in switch blocks fall through: All statements after the matching case label are executed in sequence, regardless of the expression of subsequent case labels, until a break statement is encountered. The program SwitchDemoFallThrough shows statements in a switch block that fall through. The program displays the month corresponding to the integer month and the months that follow in the year:

public class SwitchDemoFallThrough {

  public static void main(String args[]) {
    java.util.ArrayList futureMonths = new java.util.ArrayList();

    int month = 8;

    switch (month) {
      case 1: futureMonths.add("January");
      case 2: futureMonths.add("February");
      case 3: futureMonths.add("March");
      case 4: futureMonths.add("April");
      case 5: futureMonths.add("May");
      case 6: futureMonths.add("June");
      case 7: futureMonths.add("July");
      case 8: futureMonths.add("August");
      case 9: futureMonths.add("September");
      case 10: futureMonths.add("October");
      case 11: futureMonths.add("November");
      case 12: futureMonths.add("December"); break;
      default: break;

    if (futureMonths.isEmpty()) {
      System.out.println("Invalid month number");
    } else {
      for (String monthName : futureMonths) {

This is the output from the code:
Technically, the final break is not required because flow falls out of the switch statement. Using a break is recommended so that modifying the code is easier and less error prone. The default section handles all values that are not explicitly handled by one of the case sections.
The following code example, SwitchDemo2, shows how a statement can have multiple case labels. The code example calculates the number of days in a particular month:

class SwitchDemo2 {
    public static void main(String[] args) {

        int month = 2;
        int year = 2000;
        int numDays = 0;

        switch (month) {
            case 1:
            case 3:
            case 5:
            case 7:
            case 8:
            case 10:
            case 12:
                numDays = 31;
            case 4:
            case 6:
            case 9:
            case 11:
                numDays = 30;
            case 2:
                if ( ((year % 4 == 0) && !(year % 100 == 0))
                     || (year % 400 == 0) )
                    numDays = 29;
                    numDays = 28;
                System.out.println("Invalid month.");
        System.out.println("Number of Days = " + numDays);

This is the output from the code:
Number of Days = 29

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