Chapter 3: Making decisions

Question 1

Control flow statements allow applications to execute specific code segments selectively.

Answer 1

True

Question 2

A block of code in Java consists of zero or more statements enclosed in balanced braces ({}).

Answer 2

True

Question 3

The target of a decision-making statement can be a single statement or a block of statements.

Answer 3

True

Question 4

The if statement requires curly braces only when it has multiple statements.

Answer 4

True

Question 5

The else statement in Java is optional.

Answer 5

True

Question 6

Java 16 introduced pattern matching with if statements and the instanceof operator.

Answer 6

True

Question 7

Pattern matching increases boilerplate code in Java applications.
If false, why?

Answer 7

Pattern matching reduces redundant code, making it more concise.
(Answer: False)

Question 8

The pattern variable in pattern matching must be explicitly cast before use.

Answer 8

False: The instanceof check implicitly casts the variable when the condition is met.

Question 9

A pattern variable can be of the same type as the left-hand side of an instanceof expression. If false, why?

Answer 9

The instanceof check implicitly casts the variable when the condition is met.

Question 10

Pattern matching allows an instanceof expression to declare variables with a type different from the checked type.
If false, why?

Answer 10

The pattern variable must match a subtype of the checked type.

Question 11

Given Integer value = 123;, both if(value instanceof Integer) {} and if(value instanceof Integer data) {} compile successfully.
If false, why?

Answer 11

The second statement does not compile because pattern matching requires the pattern variable type to be a strict subtype of Integer.

Question 12

The traditional instanceof operator enforces the same subtype restrictions as pattern matching.
If false, why?

Answer 12

Traditional instanceof does not require the type to be a strict subtype.

Question 13

The compiler applies flow scoping when working with pattern matching.

Answer 13

True

Question 14

Flow scoping means the variable is only in scope when the compiler can definitively determine its type.

Answer 14

True

Question 15

Flow scoping is not strictly hierarchical like instance, class, or local scoping.

Answer 15

True

Question 16

A switch statement allows case values to be combined using commas.

Answer 16

True

Question 17

A switch statement does not require any case statements.

Answer 17

True

Question 18

The break statement is optional inside switch cases.

Answer 18

True

Question 19

A switch statement does not require parentheses. If false, why?

Answer 19

Parentheses are required in a switch statement.

Question 20

A switch statement does not require a beginning curly brace.

Answer 20

A beginning curly brace is mandatory.

Question 21

The default case is required in a switch statement.

Answer 21

The default case is optional.

Question 22

A break statement always terminates the switch statement.

Answer 22

If break is omitted, execution continues to the next case.

Question 23

Flow scoping works exactly like local variable scoping.

Answer 23

Flow scoping is based on program flow, not hierarchical rules.

Question 24

In pattern matching, a variable declared inside an if statement always remains in scope outside it.

Answer 24

The variable remains in scope only if the compiler guarantees its type.

Question 25

Does the default case in a Java switch statement have to be the last case?

Answer 25

No, the default case can appear anywhere in the switch block. There is no rule requiring it to be the last case.

Question 26

How does the default case behave in a switch statement?

Answer 26

It behaves like any other case label, meaning execution continues sequentially unless interrupted by a break, return, or another control flow statement.

Question 27

What happens if the default case is placed before other cases without a break?

Answer 27

Execution will fall through to the next case unless a break or other control flow statement is present.

Question 28

Can a default case fall through to another case like a regular case label?

Answer 28

Yes, if there is no break statement, execution will continue into the next case.

Question 29

Why does Java allow default to be placed anywhere in a switch block?

Answer 29

Because default is treated like a regular case label, and Java does not enforce a specific position for it.

Question 30

What primitive data types are supported in a switch statement?

Answer 30

int, byte, short, and char.

Question 31

What wrapper classes are supported in a switch statement?

Answer 31

Integer, Byte, Short, and Character.

Question 32

What non-primitive types are supported in a switch statement?

Answer 32

String, enum values, and var (if it resolves to a supported type).

Question 33

Which primitive types are not allowed in a switch statement?

Answer 33

boolean, long, float and double

Question 34

Why is boolean not allowed in a switch statement?

Answer 34

Because it has too small a range of values (only true and false).

Question 35

Why are floating-point types (float and double) not allowed in a switch statement?

Answer 35

Because they have a very wide range of possible values, making them impractical for case comparisons.

Question 36

What types of values can be used in case statements?

Answer 36

Only compile-time constant values of the same data type as the switch value.

Question 37

What are valid case statement values?

Answer 37

Literals, enum constants, or final constant variables initialized with a literal.

Question 38

Can a case statement value be determined at runtime?

Answer 38

No, case values must be compile-time constants and cannot result from method calls.

Question 39

What is a switch expression?

Answer 39

A switch construct that returns a value and must have all branches return a compatible data type.

Question 40

What is required for a switch expression to work?

Answer 40

All case and default branches must return a value of a compatible data type.

Question 41

How can case values be grouped in a switch expression?

Answer 41

By combining multiple case values using commas (e.g., case 1, 2, 3 ->).

Question 42

What are the two types of branches in a switch expression?

Answer 42

Expression branches and block branches.

Question 43

When is a default branch required in a switch expression?

Answer 43

When not all possible cases are covered, or when a value is being returned.

Question 44

What must happen if a switch expression returns a value?

Answer 44

Every branch that isn’t an expression must yield a value.

Question 45

What punctuation is required after a switch expression?

Answer 45

A semicolon (;).

Question 46

What is the size of a byte in Java?

Answer 46

A byte in Java is 8 bits (1 byte) in size.

Question 47

What is the minimum value a byte can hold in Java?

Answer 47

The minimum value of a byte in Java is -128.

Question 48

What is the maximum value a byte can hold in Java?

Answer 48

The maximum value of a byte in Java is 127.

Question 49

What happens if you assign a value outside the range of a byte in Java?

Answer 49

If you assign a value outside the byte range (-128 to 127), the compiler throws a “possible lossy conversion” error unless explicit type casting is used.

Question 50

Can you use var c[][] = new char[3][]; in Java?

Answer 50

No — you cannot combine var with array brackets on the left-hand side.

Question 51

What does var c = new char[4][]; infer the type as?

Answer 51

It infers the type as char[][].

Question 52

How should you declare a 2D array using var?

Answer 52

Use var without brackets: ``` var c = new char[3][]; ```

Question 53

Wrapper classes are allowed in switch statemenet?

Answer 53

No.