Java Switch case statement

Java has a built-in multi way decision statement known as switch statement.

When it is used?

When in our program number of alternatives increases then program becomes difficult to read(Like if else statement). It may confuse to the developer a lot. This is overcome using the switch statement.

Switch case is similar to the if else statement, But the reason for switch case use is that switch knows which case need to be executed. This is not possible in if else statement. If else has to go through all conditions

Syntax

switch ( test-expression )
{
   case const_value1:
      // case 1 statements;
   break;

   case const_value2:
      // case 2 statements;
   break;
   .
   .
   .

   case const_value N:
      // case N statements;
   break;

   default:	// same as else 
      // default block statements
   break;
}	

Flowchart

How switch statement works?

• The switch statement tests the value of a given expression against a list of case values.
• When a match is found, a block of statements associated with that case is executed.
• If the expression doesn’t match any case value in the switch statement, then compiler enters into the default block statement.

Example - Check entered character is Vowel or Consonant using switch case.

Vowel - it is speech sound produced when breath flows out through the mouth without being blocked by the teeth, tongue, or lips. Ex - a,e,i,o,u

Consonant - it is speech sound produced by completely or partly stopping the air being breathed out through the mouth. Ex- except Vowels all others are Consonants.

public class SwitchDemo
{
    public static void main(String[] args) 
    {
	char mychar = 'i';
	String result;
	switch(mychar)
	{
	    case 'a':
		result = "Vowel";
	    break;
		
	    case 'e':
		result = "Vowel";
	    break;
		
	    case 'i':
		result = "Vowel";
	    break;
		
	    case 'o':
		result = "Vowel";
	    break;
		
	    case 'u':
		result = "Vowel";
	    break;
		
	    default:
		result = "Consonant";
	    break;
	 }
	 System.out.println("Given character is "+result);
    }
}

Output

In above example first of all condition is checked using mychar variable, the compiler searched for the matching case statement in the block of code. if case is matched then result variable is assigned.

Different ways of switch case

We can write the switch case statement in different ways.

1. Without using break statement

We can write above program for checking vowels and consonant as.

public class SwitchNoBreak
{
    public static void main(String[] args) 
    {
	char mychar = 'u';
	String result;
	switch(mychar)
	{
	    case 'a':
			
	    case 'e':
		
	    case 'i':
			
	    case 'o':
			
	    case 'u':
		result = "Vowel";
	    break;
		
	    default:
		result = "Consonant";
			
	 }
	 System.out.println("Given character is "+result);
    }
}

Output