🕹️ Practice arcade

🐛 Bug-Hunt Time Trial

Two minutes. Each method has one bad line: an int average, a <= that runs off the end, a max that starts at 0, == on strings. Find it.

➗ Operator Sprint

Integer division, overflow, casts, char arithmetic, ++, precedence and short-circuit guards. Two minutes, as many as you can.

🔤 Strings Sprint

indexOf and substring, results thrown away, == against equals. Two minutes of String methods.

🌊 Streams Sprint

filter, map, sorted, skip and limit in order, reduce with its identity, and which functional interface a job needs. Two minutes.

💥 Null, Throw, Crash

width = width, a map get that unboxes null, an exception built but never thrown, remove(int) on a list of IDs, Optional.of(null). Three misses and you're out.

🔗 Copies and References

Aliased arrays, clones, pass-by-value with ints, arrays and Strings, static fields, == against equals on objects. Three misses and you're out.

🗃️ Collections Survival

remove(int) against remove(Object), put on a key that's there, queue or stack, TreeSet order, and which collection fits. Three misses and you're out.

🧪 Lambdas and Lookups Survival

A TreeSet that ignores case, a TreeMap that counts, a lazy stream with peek, andThen against compose, and orElse that runs anyway. Three misses and you're out.

🔁 Loop Tracer

Trace switches, while and do-while loops, for loops, break and continue. Five right in a row.

📞 Calls and Overloads

Which overload a call picks, and what a recursive method prints on the way down and on the way back. Five in a row.

🧱 Objects Mastery

Constructor chains, overrides against overloads, enum ordinals. Five right in a row.

🪞 Object Models Mastery

Two names for one object, a constructor that assigns a parameter to itself, which default method runs, and a record that never changes. Five in a row.

🧯 Exceptions Mastery

Which exception a line throws, what finally prints and when, and the order try-with-resources closes things. Five in a row.