Slide 9.8: The switch statement (cont.): String cases

Slide 9.7: The switch statement
Slide 9.9: The break statement
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The switch Statement (Cont.)

String in Switch Cases
We can use a string literal/constant to control a switch statement, which is not possible in C/C++. Using a string-based switch is an improvement over using the equivalent sequence of if/else statements:

Expensive operation: Switching on strings can be more expensive in term of execution than switching on primitive data types. Thus, it is best to switch on strings only if the controlling data is already in string form.

String should not be NULL: Ensure that the expression in any switch statement is not null while working with strings to prevent a NullPointerException from being thrown at run-time.

Case sensitive comparison: The switch statement compares the String object in its expression with the expressions associated with each case label as if it were using the String.equals() method; consequently, the comparison of String objects is case sensitive.

Better than if-else: The Java compiler generates generally more efficient bytecode from switch statements that use String objects than from chained if-then-else statements.

StringCase.java (string cases in a switch statement)

// Demonstration of the use of string cases in a switch statement
public class StringCase { 
  public static void main( String[ ] args ) { 
    switch( args[0] ) { 
      case "Monday": 
        System.out.print( args[0].compareTo("Monday") ); 
        break;
      case "Tuesday":
        System.out.print( args[0].contains("day") );
        break;
      case "Wednesday":
        System.out.print( args[0].equals("Wednesday") );
        break;
      case "Thursday":
        System.out.print( args[0].indexOf("day") );
        break;
      case "Friday":
        System.out.print( args[0] == "Friday" );
        break;
      default: 
        System.out.print( args[0] != "Sunday" ); 
    } 
  }
}

shell> java StringCase

Output: Result:

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Slide 9.7: The switch statement
Slide 9.9: The break statement
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