I want to store key-value pairs in TreeMap and sort the entries based on the value of key as per the following logic: “type” (case insensitive) key should be at first. the key start with “metadata” (case insensitive) should be at last in ascending order rest of the keys(case insensitiv…
Tag: comparator
LinkedList inside a LinkedList iteration in java
Im trying to iterate a Linked List inside of a linked list but I’m not sure how to proceed with it. I’m used to using a passed parameter for what will be iterated but when I’m iterating a linked list …
Why compareTo throws NPE using a comparator who doesn’t do that when user separatedly
I created a comparator that never throws NPE. However, when using it inside compareTo, it throws NPE. Why? When expliciting the comparator on Collections.sort call, sort operation doesn’t use compareTo implementation, as expected. When not doing this, sort operation uses the implementation of compareTo.…
Sort List of string arrays by first element
I want to sort a list of string arrays by first element in each array element of same list, in reverse order, so 2, 1, 0 Here’s what i tried so far: The problem is that at sorted line i have an error highlighted, saying: “sorted(java.util.List, java.util.Comparator Answer Stream.sorted() takes a c…
understanding comparator in Collections.max
Can somebody please explain what the following lines of code mean?. I had a hard time understanding the Comparator part.I tried googling but all of them were too complex for me to understand. Could somebody please explain it in simpler way? Answer The max method returns the element that is considered the R…
Java: ArrayList sorting using comparators (ArrayLists doesn’t store objects)
I want to sort an ArrayList of type String using a comparator. I have only found examples on how to do it if an ArrayList stores objects. I have an ArrayList of strings that have 10 symbols and last 5 of those symbols are digits that form a number. I want to solve an array list in ascending order of
What is the equivalent way to do Ordering.lexicographical() in Java 8 Comparator?
Is there a way to implement Ordering.lexicographical() with Java 8 Comparator? Comparator.thenCompare seems to be limited in this Answer Seemingly not, no. As a result, Guava still provides this functionality, but in the new class Comparators: https://guava.dev/releases/snapshot/api/docs/com/google/common/col…
Java sorting is not the same with MySQL sorting
I need to check the sorting in the table and table content is given by MySQL. I’m trying the following: Collections.sort(sorted, String.CASE_INSENSITIVE_ORDER); And get the following result: tes3@test.com test4@test.com test5@test.com test@test.com test_user@mail.com user-og@driver.com And this is what …
TreeSet constructor with Comparator parameter
In Java’s documentation for its class TreeSet one of the constructors is shown to have the following header: Can someone help explain why there is a constructor for TreeSet which takes a comparator object as its argument? I have no clue why this is done. Answer The elements in a TreeSet are kept sorted. If yo…
how to test Comparator at junit test
I need to test this method – compare(). Can You get advice? How better I can do this(all part if, else-if, else). After this recomendations – we have next picture (Thank YOU guys a lot!): All is normal testing now. Answer Just instantiate your comparator class and pass in objects: