Which method does the compiler NOT generate for record Point(int x, int y) {}?
Record fields are final; there are no setters. Accessors are named after the components.
QuizzesModern Java
Modern Java (17–21)
Records, sealed types, pattern matching, switch expressions, var, text blocks and sequenced collections.
14 questions
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Question 1 of 14Score 0
Which method does the compiler NOT generate for
What does this print?
record Point(int x, int y) {}
System.out.println(new Point(1, 2).equals(new Point(1, 2)));Records generate value-based equals and hashCode from all components.
Which of these can a record declare?
Records may have static members, instance methods and implement interfaces — but no extra instance fields or superclass.
A record has a List<String> component. How do you make it effectively immutable?
Records are only shallowly immutable — defensively copy mutable components.
Each permitted subclass of a sealed class must be declared…
Every permitted subtype must state how the hierarchy continues. Records are implicitly final.
Why does this switch need no default branch?
sealed interface Shape permits Circle, Square {}
record Circle(double r) implements Shape {}
record Square(double s) implements Shape {}
double area(Shape sh) {
return switch (sh) {
case Circle c -> Math.PI * c.r() * c.r();
case Square s -> s.s() * s.s();
};
}Sealed hierarchies make pattern switches exhaustive; adding a new permitted type makes this stop compiling.
What does a pattern-matching switch do with a null selector when there is no case null?
Add case null -> (or case null, default ->) to handle it explicitly.
Which keyword returns a value from a block inside a switch expression?
yield produces the value of a switch-expression block; return would return from the enclosing method.
Which line compiles?
var needs an initialiser with a known type and works only for local variables.
Inside a text block, what does a backslash at the end of a line do?
The line-continuation escape is handy for long SQL strings; \s keeps a trailing space.
What does this print?
Object o = 42;
if (o instanceof Integer i && i > 40) {
System.out.println(i + 1);
}Pattern matching for instanceof binds i where the match is definitely true, including the right side of &&.
Which Java 21 API returns the last element of a LinkedHashSet directly?
Sequenced collections add getFirst, getLast, addFirst, addLast, removeFirst, removeLast and reversed().
What is wrong with case CharSequence cs -> appearing before case String s ->?
More specific patterns must come before more general ones (dominance).
Which Java version made virtual threads a final (non-preview) feature?
Virtual threads previewed in 19 and 20 and became final in Java 21 (JEP 444).
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