Recent questions tagged collections

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collections - Python defaultdict and lambda

In someone else's code I read the following two lines: x = defaultdict(lambda: 0) y = defaultdict(lambda: ... figure out what it is exactly. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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748 views

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collections - What is the time complexity performance of HashSet.contains() in Java?

I'm tempted to think that the HashSet.contains(Object) method performs in constant time. It simply gets the hash code ... when it only has one? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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651 views

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collections - val-mutable versus var-immutable in Scala

Are there any guidelines in Scala on when to use val with a mutable collection versus using var with an immutable ... how to make that choice. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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612 views

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collections - Limit size of Queue<T> in .NET?

I have a Queue<T> object that I have initialised to a capacity of 2, but obviously that is just the ... to create my own inherited class? See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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787 views

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collections - Is it possible in java make something like Comparator but for implementing custom equals() and hashCode()

I have an array of objects and I want to concatenate it with another array of objects, except that objects ... Comparator, but for equals. See Question&Answers more detail:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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501 views

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collections - What is this &:last Ruby construct called?

This question already has answers here: Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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634 views

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collections - Iterating through a list in reverse order in java

I'm migrating a piece of code to make use of generics. One argument for doing so is that the for loop is ... I can't add any new dependencies outside the JDK. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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650 views

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collections - What is the best way get the symmetric difference between two sets in java?

I'm wondering if there is a quick/clean way to get the symmetric difference between two sets ? I have: ... ] Just to clarify I need the symmetric difference. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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718 views

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collections - How can I initialize an ArrayList with all zeroes in Java?

It looks like arraylist is not doing its job for presizing: // presizing ArrayList<Integer> list = new ArrayList<Integer> ... an exact size like what C++ does? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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603 views

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collections - How to copy a java.util.List into another java.util.List

I have a List<SomeBean> that is populated from a Web Service. I want to copy/clone the contents of that ... into another List? Not through iteration, of course. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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728 views

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collections - Size-limited queue that holds last N elements in Java

A very simple & quick question on Java libraries: is there a ready-made class that implements a Queue with a ... one in Apache Commons or something like that? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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584 views

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collections - How can I create a Set of Sets in Python?

I'm trying to make a set of sets in Python. I can't figure out how to do it. Starting with the empty set xx: xx ... ..., An would "cancel" two sets if Ai = Aj) Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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780 views

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collections - Java Ordered Map

In Java, Is there an object that acts like a Map for storing and accessing key/value pairs, but can return an ordered ... ); Assert(om.get(key) == value); } Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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620 views

1 answer

collections - Easiest way to convert a List to a Set in Java

What is the easiest way to convert a List to a Set in Java? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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613 views

1 answer

collections - Is there a common Java utility to break a list into batches?

I wrote myself a utility to break a list into batches of given size. I just wanted to know if there is ... if there any existing utility already for the same. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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937 views

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collections - Java 8 Nested (Multi level) group by

I have few classes like below class Pojo { List<Item> items; } class Item { T key1; List<SubItem> subItems ... on fields in the same object as discussed here Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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568 views

1 answer

collections - How to convert an Array to a Set in Java

I would like to convert an array to a Set in Java. There are some obvious ways of doing this (i.e. with a ... : java.util.Arrays.asList(Object[] a); Any ideas? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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668 views

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collections - How do I overload the square-bracket operator in C#?

DataGridView, for example, lets you do this: DataGridView dgv = ...; DataGridViewCell cell = dgv[1,5]; ... you supply it with invalid coordinates. Fair warning. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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604 views

1 answer

collections - How to force max to return ALL maximum values in a Java Stream?

I've tested a bit the max function on Java 8 lambdas and streams, and it seems that in case max is executed, even if ... ); // Would print 5, 5 in any order. Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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663 views

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collections - Why should the interface for a Java class be preferred?

PMD would report a violation for: ArrayList<Object> list = new ArrayList<Object>(); The violation was "Avoid ... latter with List be used instead of ArrayList? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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625 views

1 answer

collections - How can I turn a List of Lists into a List in Java 8?

If I have a List<List<Object>>, how can I turn that into a List<Object> that contains all the objects in ... iteration order by using the features of Java 8? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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573 views

1 answer

collections - What are the differences between a HashMap and a Hashtable in Java?

What are the differences between a HashMap and a Hashtable in Java? Which is more efficient for non-threaded applications? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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731 views

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collections - Java 8 Distinct by property

In Java 8 how can I filter a collection using the Stream API by checking the distinctness of a property of each ... class is it possible to do this succinctly? Question&Answers:os...

asked Oct 17, 2021 in Technique[技术] by 深蓝 (71.8m points)

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593 views

1 answer

collections - How do i filter and copy values to a list of objects based on another list in Kotlin

I am trying to filter a list of objects based on a certain condition from a second list and then update/copy certain ... values-to-a-list-of-objects-based-on-another-list-in-ko...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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585 views

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collections - Convert List<List<Object>> to Map<Object,List<Object>> Java8

I have a Object class Wrapper{ private SomeObject someObject; private String value; } class SomeObject{ ... /questions/65846405/convert-listlistobject-to-mapobject-listobject-java8...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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613 views

1 answer

collections - Take while running total smaller than value

I am trying to generate a list of even integers while the sum of the items in the list is less ... stackoverflow.com/questions/65850132/take-while-running-total-smaller-than-value...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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902 views

1 answer

collections - Fetch list of objects in one list that are not part of another list using Java stream filter

This question already has answers here: question from:https://stackoverflow.com/questions/65889447/fetch-list-of-objects-in-one-list-that-are-not-part-of-another-list-using-java-s...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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705 views

1 answer

collections - Merge two maps with same keys in java and add the value together

Closed. This question needs details or clarity. It is not currently accepting answers. question from:https://stackoverflow. ... -with-same-keys-in-java-and-add-the-value-together...

asked Oct 7, 2021 in Technique[技术] by 深蓝 (71.8m points)

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