Question

State whether each of the following is true or false. If false, explain why. a) The default case is required in the switch selection statement. b) The break statement is required in the last case of a switch selection statement. c) The expression ( ( x > y ) && ( a < b ) ) is true if either x > y is true or a < b is true. d) An expression containing the || operator is true if either or both of its operands are true. e) The comma (,) formatting flag in a format specifier (e.g., %,20.2f) indicates that a value should be output with a thousands separator. f) To test for a range of values in a switch statement, use a hyphen (–) between the start and end values of the range in a case label. g) Listing cases consecutively with no statements between them enables the cases to perform the same set of statements.

Short answer

a) False, b) False, c) False, d) True, e) True, f) False, g) True.

Step-by-step solution

Evaluate statement a

The statement says the default case is required in the switch statement. This is false. A switch statement can function without a default case, although including it is good practice to handle unexpected values.

Evaluate statement b

This statement suggests that the break statement is required in the last case of a switch statement. This is false. While the break statement is typically used to exit the switch after a case is executed, it is not required and omitting it will cause the flow to fall through to the next case.

Evaluate statement c

The statement claims that the expression \( ( ( x > y ) \&\& ( a < b ) ) \) is true if either \( x > y \) is true or \( a < b \) is true. This is false because the expression uses the logical AND (&&) operator, which means both conditions must be true for the whole expression to be true.

Evaluate statement d

This statement asserts that an expression with the || operator is true if either or both operands are true. This is true. The logical OR (||) operator only requires one of the operands to be true for the whole expression to be true.

Evaluate statement e

The statement suggests that the comma (,) in a format specifier indicates a value should be output with a thousands separator. This is true. In many programming languages, including Java and C#, the comma is used as a grouping separator in formatted strings.

Evaluate statement f

The statement claims the way to test for a range of values in a switch statement is to use a hyphen between start and end values. This is false. Switch statements cannot directly handle ranges using a hyphen; each case must be stated explicitly, or logic needs to be implemented in the case blocks.

Evaluate statement g

The statement says listing cases consecutively with no statements between them enables the cases to perform the same set of statements. This is true. In switch statements, falling through from one case to another (no break statement) allows multiple cases to execute the same block of code.

Key concepts

switch statement

A switch statement is a powerful control structure in Java used to execute one block of code among many choices, based on the value of an expression. It can be more readable than a chain of if-else statements when dealing with a variable that can hold several discrete values. In a switch statement, the expression is evaluated once, and the result is compared with the values of each case. If a match is found, the corresponding block of code is executed.
By design, a switch statement can include a special case called "default," which is executed if none of the case values matches the switch expression. While it's not mandatory to include a default case, it's considered a good practice. This ensures that you handle unexpected values effectively.

• Use a switch when you need to compare a single variable against multiple values.
• A switch expression should be of type byte, short, int, char, String or an enumeration.
• If no cases match and there's no default case, the control goes to the statement after the switch.

logical operators

Logical operators in Java are used to form complex logical expressions by combining multiple conditions. They are essential for decision-making processes and control flow in programming. Two primary logical operators are the logical AND (&&) and the logical OR (||). Each serves a unique purpose:
The AND operator, &&, connects two conditions in such a way that the combined expression is true only if both conditions are true. For instance, the expression \( (x > y) \&\& (a < b) \) would evaluate to true only if both x is greater than y and a is less than b.
The OR operator, ||, is more lenient; it returns true if at least one of its operands is true. So the expression \( (x > y) || (a < b) \) would be true if either x is greater than y or a is less than b, or if both are true.

• Use && when requiring all conditions to be true.
• Use || when only one or more conditions need to be true.

format specifiers

Format specifiers in Java help in formatting output to make it more readable and standardized. They define the layout of textual and numerical data. Just like how printf works in C, Java's printf method also uses format specifiers. For example, the specifier %,20.2f formats a floating-point number. Here, '20' is the width of the field, and '2' specifies the number of decimal places. Additionally, including a comma in %.20,2f specifies that numbers are displayed with thousands separators for improved readability.
Understanding format specifiers improve the visual representation of numerical data in software output, making it easier to read by adding padding, specifying decimal precision, or applying other styles.

• Use format specifiers to control numeric and string formatting.
• The comma separates thousands in large numbers, e.g., 1,000.
• Precision and field width in specifiers enhance data presentation.

range testing in switch

Normally, the switch statement is used for checking specific case values rather than ranges. This can be limiting if you want to execute the same block for a range of values. A common misconception is the belief that a hyphen can be used to denote a range, like in case 1-5. This, however, is not possible in Java.
To handle ranges in a switch statement, logic needs to be inserted within the case blocks. This means using additional code such as if-else statements inside each case to check if a value falls within a particular range.

• Specify each case individually or use logic within cases for ranges.
• Consider alternate structures like if-else for extensive range checking.
• Switch is best for discrete values; not an ideal tool for ranges.