Highly likely from Josh Bloch §: I did write these methods, so I suppose I’m qualified to answer. It is true that there is no single best sorting algorithm. QuickSort has two major deficiencies when compared to mergesort: It’s not stable (as parsifal noted). It doesn’t guarantee n log n performance; it can degrade to … Read more
The API guarantees a stable sorting which Quicksort doesn’t offer. However, when sorting primitive values by their natural order you won’t notice a difference as primitive values have no identity. Therefore, Quicksort can used for primitive arrays and will be used when it is considered more efficient¹. For objects you may notice, when objects with … Read more
Complicated question. Let’s see what happens. You instantiate a new instance, which is backed with new array. So, garbage collector should clear all the key and values from the previous map, and clear the reference to itself. So O(n) algorithm is executed anyway, but in the garbage collector thread. For 1000 records you won’t see … Read more
Yes. ArrayList is a sequential list. So, insertion and retrieval order is the same. If you add elements during retrieval, the order will not remain the same.
Pretty common question, this one. The hard thing is finding the duplicates. You should strive for referential transparency. What that means is that, if I have an expression “e”, I could make a val x = e, and replace e with x. This is the property that mutability break. Whenever you need to make a … Read more
Method references can be used when you have a method (or constructor) that fits the shape of the target you’re trying to satisfy. You can’t use a method reference in this case because the shape you’re targeting is a Supplier, which takes no arguments, but what you have is a TreeSet constructor, which does take … Read more
The .NET 4.0 class that supports concurrency is named ConcurrentDictionary.
Simply, Dictionary<TKey,TValue> is a generic type, allowing: static typing (and compile-time verification) use without boxing If you are .NET 2.0 or above, you should prefer Dictionary<TKey,TValue> (and the other generic collections) A subtle but important difference is that Hashtable supports multiple reader threads with a single writer thread, while Dictionary offers no thread safety. If … Read more
for (Iterator<String> iter = list.listIterator(); iter.hasNext(); ) { String a = iter.next(); if (…) { iter.remove(); } } Making an additional assumption that the list is of strings. As already answered, an list.iterator() is needed. The listIterator can do a bit of navigation too. –——— Update As @AyushiJain commented, there is list.removeIf(…);
(originally from Ways to sort lists of objects in Java based on multiple fields) Original working code in this gist Using Java 8 lambda’s (added April 10, 2019) Java 8 solves this nicely by lambda’s (though Guava and Apache Commons might still offer more flexibility): Collections.sort(reportList, Comparator.comparing(Report::getReportKey) .thenComparing(Report::getStudentNumber) .thenComparing(Report::getSchool)); Thanks to @gaoagong’s answer below. Note … Read more