mediumstream pipelines
Which list is produced by mapping toLowerCase?
List<String> r = Stream.of("A","B","C").map(String::toLowerCase).toList();why this works
Built for Java mastery, not memorisation.
Every question is hand-checked, every answer comes with an explanation, and your progress builds into a clear picture of where you stand.
The snippet is on the page
Every Java question shows its code before you answer, so you are reading real Java, not a description of it.
A written explanation, always
Once you attempt a question you get the reasoning, not just a tick. That matters most on Java, where collections behaviour, equals and hashcode contracts, string interning, checked versus unchecked exceptions, stream laziness, and the concurrency primitives.
Your weak topics, named
Progress is tracked per topic across the 44 Java topics, so revision points at the gaps instead of the whole list.
faq
Things people ask.
How many Java MCQs are on Journey Uncommon?
541 Java questions right now: 112 easy, 211 medium and 218 hard. That number is read straight from the question table when this page is built, so it is never a rounded marketing figure.
Do I need an account to read the Java questions?
No. Every Java question, including its code snippet, its difficulty and its topic, is readable without signing in. You need a free account only to submit an answer, see which option is correct, and read the worked explanation. We keep it that way so the platform stays honest about what you actually got right.
What do Java interviewers actually test?
Collections behaviour, equals and hashCode contracts, string interning, checked versus unchecked exceptions, stream laziness, and the concurrency primitives.
Which Java topics are covered?
44 distinct topics are tagged on the Java questions, including stream pipelines, primitives and char width, if switch loops, try-with-resources, main entry point, final and constants. The topic labels come from the questions themselves, so the list matches what you will actually be asked.
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Where is Java used in real jobs?
Banking, large-scale services, Android, and any company running Spring in production.
What a Java question here actually looks like
These are 12 of the 541 Java questions in the library, pulled live from the question table. The snippet, the difficulty and the topic are all here. The answer options and the explanation are not. Those need a free account.
Collections behaviour, equals and hashCode contracts, string interning, checked versus unchecked exceptions, stream laziness, and the concurrency primitives.
Sample Java MCQs
hardprimitives and char width
What value of i is printed after two post-increments?
int i = 5; int s = i++ + i++; System.out.println(i);mediumpattern matching switch instanceof
Using record deconstruction patterns, what does `format(new Point(1, 2))` print?
record Point(int x, int y) {}
static String format(Object o) {
return switch (o) {
case Point(int x, int y) -> "x+y=" + (x + y);
default -> "?";
};
}hardstream pipelines
What count does iterate(1, i->i*2).limit(3) produce?
long c = IntStream.iterate(1, i -> i*2).limit(3).count();\nSystem.out.println(c);mediumclass loading delegation
What is the result of executing this code?
class A {\n static { System.out.print("A"); }\n A() { System.out.print("B"); }\n}\nnew A();mediumif switch loops
What does this code print?
int x = 5;\nx = x++;\nSystem.out.println(x);mediumInteger caching identity
What does this code print?
Integer a = 200;\nInteger b = 200;\nSystem.out.println(a == b);mediumif switch loops
What does this code print?
int x;\nif (false) x = 5;\nSystem.out.println(x);hardLambdas and method refs
What does this code do?
List<Supplier<Integer>> ss = new ArrayList<>();\nfor (int i = 0; i < 3; i++) { ss.add(() -> i); }medium== vs equals
What does this code print?
String a = new String("x");\nString b = new String("x");\nSystem.out.println(a.equals(b));mediumstream pipelines
What does this code print?
System.out.println(IntStream.range(0,3).reduce(0, Integer::sum));mediumCompletableFuture composition
What does this code print?
CompletableFuture<Integer> f = CompletableFuture.completedFuture(5);\nSystem.out.println(f.get());Sign in to answer
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Where Java shows up
Banking, large-scale services, Android, and any company running Spring in production.