Chapter 3: Making decisions Flashcards
Control flow statements allow applications to execute specific code segments selectively.
True
A block of code in Java consists of zero or more statements enclosed in balanced braces ({}).
True
The target of a decision-making statement can be a single statement or a block of statements.
True
The if statement requires curly braces only when it has multiple statements.
True
The else statement in Java is optional.
True
Java 16 introduced pattern matching with if statements and the instanceof operator.
True
Pattern matching increases boilerplate code in Java applications.
If false, why?
Pattern matching reduces redundant code, making it more concise.
(Answer: False)
The pattern variable in pattern matching must be explicitly cast before use.
False: The instanceof check implicitly casts the variable when the condition is met.
A pattern variable can be of the same type as the left-hand side of an instanceof expression. If false, why?
The instanceof check implicitly casts the variable when the condition is met.
Pattern matching allows an instanceof expression to declare variables with a type different from the checked type.
If false, why?
The pattern variable must match a subtype of the checked type.
Given Integer value = 123;, both if(value instanceof Integer) {} and if(value instanceof Integer data) {} compile successfully.
If false, why?
The second statement does not compile because pattern matching requires the pattern variable type to be a strict subtype of Integer.
The traditional instanceof operator enforces the same subtype restrictions as pattern matching.
If false, why?
Traditional instanceof does not require the type to be a strict subtype.
The compiler applies flow scoping when working with pattern matching.
True
Flow scoping means the variable is only in scope when the compiler can definitively determine its type.
True
Flow scoping is not strictly hierarchical like instance, class, or local scoping.
True
A switch statement allows case values to be combined using commas.
True
A switch statement does not require any case statements.
True
The break statement is optional inside switch cases.
True
A switch statement does not require parentheses. If false, why?
Parentheses are required in a switch statement.
A switch statement does not require a beginning curly brace.
A beginning curly brace is mandatory.
The default case is required in a switch statement.
The default case is optional.
A break statement always terminates the switch statement.
If break is omitted, execution continues to the next case.
Flow scoping works exactly like local variable scoping.
Flow scoping is based on program flow, not hierarchical rules.
In pattern matching, a variable declared inside an if statement always remains in scope outside it.
The variable remains in scope only if the compiler guarantees its type.
Does the default case in a Java switch statement have to be the last case?
No, the default case can appear anywhere in the switch block. There is no rule requiring it to be the last case.
How does the default case behave in a switch statement?
It behaves like any other case label, meaning execution continues sequentially unless interrupted by a break, return, or another control flow statement.
What happens if the default case is placed before other cases without a break?
Execution will fall through to the next case unless a break or other control flow statement is present.
Can a default case fall through to another case like a regular case label?
Yes, if there is no break statement, execution will continue into the next case.
Why does Java allow default to be placed anywhere in a switch block?
Because default is treated like a regular case label, and Java does not enforce a specific position for it.
What primitive data types are supported in a switch statement?
int, byte, short, and char.
What wrapper classes are supported in a switch statement?
Integer, Byte, Short, and Character.
What non-primitive types are supported in a switch statement?
String, enum values, and var (if it resolves to a supported type).
Which data types are NOT allowed in a switch statement?
boolean, long, float, and double (including their wrapper classes).
Why is boolean not allowed in a switch statement?
Because it has too small a range of values (only true and false).
Why are floating-point types (float and double) not allowed in a switch statement?
Because they have a very wide range of possible values, making them impractical for case comparisons.
What types of values can be used in case statements?
Only compile-time constant values of the same data type as the switch value.
What are valid case statement values?
Literals, enum constants, or final constant variables initialized with a literal.
Can a case statement value be determined at runtime?
No, case values must be compile-time constants and cannot result from method calls.
What is a switch expression?
A switch construct that returns a value and must have all branches return a compatible data type.
What is required for a switch expression to work?
All case and default branches must return a value of a compatible data type.
How can case values be grouped in a switch expression?
By combining multiple case values using commas (e.g., case 1, 2, 3 ->).
What are the two types of branches in a switch expression?
Expression branches and block branches.
When is a default branch required in a switch expression?
When not all possible cases are covered, or when a value is being returned.
What must happen if a switch expression returns a value?
Every branch that isn’t an expression must yield a value.
What punctuation is required after a switch expression?
A semicolon (;).
What is the size of a byte in Java?
A byte in Java is 8 bits (1 byte) in size.
What is the minimum value a byte can hold in Java?
The minimum value of a byte in Java is -128.
What is the maximum value a byte can hold in Java?
The maximum value of a byte in Java is 127.
What happens if you assign a value outside the range of a byte in Java?
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.
Can you use var c[][] = new char[3][]; in Java?
No — you cannot combine var with array brackets on the left-hand side.
What does var c = new char[4][]; infer the type as?
It infers the type as char[][].
How should you declare a 2D array using var?
Use var without brackets:
var c = new char[3][];
