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Java two collections contains any
Large two collections A and B contain best best approach in these
1) Collections.disjoint(A, B)
2) org.springframework.util.CollectionUtils
CollectionUtils.containsAny(A,B)
Looking at their respective source codes, it looks like Collections.disjoint is smarter about when its arguments are Sets and have fast contains implementations, and CollectionUtils is a little smarter about checking if either collection is empty, but that's generally a smaller win.
Based on that, I'd use Collections.disjoint, which I'd tend to do anyway just because it's built-in.
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object Test extends App {
val i: Iterable[(String, Long)] = List(("a", 1), ("b", 2))
val sortedMap: SortedMap[String, Long] = i.toList.sortBy(_._2)
}
I don't want to convert Iterable to List/Array etc since it's coming form a jdbc query.
You can't do that. SortedMap sorts by keys, not values.
If you want it sorted by value, you gotta use ListMap, and can't avoid converting to List:
ListMap(i.toList.sortBy(-_._2):_*)
There isn't really too much wrong with converting to list, since you are loading the whole thing in memory anyway. This is faster too, than building a tree one element at a time.
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The thing is I need to create an unidimensional array that represents a certain number of objects.
Those objects are organized as shown in the picture.
Link
And I have to be able to tell wich one is conected to.
The number of objects is the only thing given.
Is there any algorithm of some sort to do this?
This sort of organization is often used to implement heaps in arrays: https://www.geeksforgeeks.org/array-representation-of-binary-heap/
You just put the objects into the array in level order (top 1 first, then the 2 from level 2, then the 4 from level 3, etc.).
Assuming 0-based indexing, then, the object in array[i] has children array[2*i+1] and array[2*i+2].
If your array starts at [1], then the object in array[i] has children array[2*i] and array[2*i+1]
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What is Java stream API alternative to LambdaJ indexing? Let's say I have code like this
List<Product> products = ...
Map<Month, Product> productsOnMonths = Lambda.index(products, Lambda.on(Product.class).getMonth());
Where I know that every product has unique month attribute.
products.stream().collect(Collectors.toMap(Product::getMonth, s -> s));
The difference here is that Collectors.toMap can take a third argument that says how to merge two entries when they are the same; I don't think lambdaj offers that
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In many programming languages, the array index begins with 0. Is there a reason why it was designed so?
According to me, it would have been more convenient if the length of the array was equal to the last index. We could avoid most of the ArrayIndexOutOfBounds exceptions.
I can understand when it comes to a language like C. C is an old language and the developers may have not thought about the issues and discomfort. But in case of modern languages like java, they still had a chance to redefine the design. Why have they chosen to keep it the same?
Is it somehow related to working of operating systems or did they actually wanted to continue with the familiar behaviour or design structure (though new programmers face a lot of problems related to this)?
An array index is just a memory offset.
So the first element of an array is at the memory it is already pointing to, which is simply
*(arr) == *(arr+0).
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it is possible to assign that big number in java? i need to make a calculation of 39 digits value. could any help? Thanks
Problem:
Consider the following composite number:
340282367237851113557325445936183246849
Write a Java method to find two numbers whose product is the above number.
I guess you need to check out the BigInteger of the java API. That might be able to store your results of those much big numbers. Read the documentation,
http://docs.oracle.com/javase/7/docs/api/java/math/BigInteger.html