Before going for the solution please check your if condition. I think you ought to draw a diagram of what you are doing, on paper, with before and after states. You can use an ArrayList to keep the elements in the order you want, and a HashSet to check whether an element is already present. I've been asked to do the same procedure but instead of Set, to use Map. So, unless you override the equals and hashCode methods in the classes you design, you will not be able to use them effectively with collections. I hope this helps without giving too much away.
So yes, that seems to be good. Code: Now that we know how to solve this problem of missing numbers in unsorted integer array with duplicates, it's time to turn this solution into a code and working Java program. I am searching for sortable I mean sorting after initialization and many times using Comparator Java class collection without duplicates. As you know, HashSet and LinkedHashset maintain only unique elements. It isn't a black hole at all, but an opportunity to rise to the challenge. I need to remove the duplications and end up with an array that has one instance of each unique. HashSet first uses the result of hashCode to find the bucket the element should be in.
I need to have an array that has strings in it, even if those strings are duplicates. I am also in the process of learning. In any case, once you finish running through the file, the WordMap is already in the correct form that you wanted. And there is no braces for the if condition. Timer, this is just new Date , I put it into a separate method because I was tired of copy-pasting it. With regard to Freds remarks: okay, but if you have a list 'toBeRemoved', then you must also think of how to apply this: is a removeAll suitable? Just , insert them into HashSet using add method and check return value. Depending on the nature of the application, it may well be acceptable or even desireable to sort the elements in addition to removing duplicates.
Java Program to removed duplicates from ArrayList Here is our sample program to learn how to remove duplicates from ArrayList. I'd be grateful for anybody who could point me to the right direction. That would be interesting to see. If the list you are given is not sorted, then you can sort it yourself, or you'll need some sort of collection to keep track of which animals you've already seen. Nothing happens to this Stream until you use the final Stream operation to create the List.
Timer, this is just new Date. I think you're right about the caps lock. If that is true, you can add to the List. So, ain't throwing in the towel by any means! Scott Apart from using HashSet you can use nested loops to check if there is any duplicate element in the arraylist. If you use a LinkedHashMap rather than an ordinary HashMap, get the order of insertion maintained in your new List.
Hello, So, as the title says I'm trying to count the number of elements in an ArrayList which also have duplicates. As you read each word, pass it to the WordMap to be added to the Map: wordMap. Then you might be better able to see what you want. If they exist, delete them. My code works because the lists which the website uses as tests only contain a maximum of 1 duplicate per word. Do you need to modify your original list? How you do that depends on how formal they want you to be about the problem.
Get used to them :- Either approach is valid. It is the general purpose hash table implementation in Java. Though there are multiple ways to do this, I think using LinkedHashSet is the simplest one because its simple and also preserve the order of elements. Thank you all for your help. Making something faster, might mean making it harder to understand. The teacher has a register with names of all students, he goes through the list and mark absences on red.
This is the first time I have ever used this method so if it's not right, I apologize. Is there some kind of regex thing I could use or something? If they exist, delete them. For a list of 100,000 objects, TreeSet gets slower when more than about 3500 are unique. Thank you very much for your valuable replies. This method will work on any type of Java array e.
I'm going to type how I'm able to explain it, maybe somebody else can help clean up my verbose attempt. Btw, if you are not familiar with array and essential data structure e. Memory usage vs speed vs amount of code required vs ease of understanding the code - there is always a trade-off You will normally have to compromise on some the above somewhere along the way. Here is your original code adapted to work. Thanks for all the help and replies from everybody else, it's been great food for thought. Another method is to put all the elements into a counting application if you search for Java® Tutorials Map interface you will find one there. Anyway, off to get my litre of and cup of tea and have a think.
Things are going along and I'm able to find most things via Google. I changed to Integers for no real reason. So the Set contains one copy of each word in the List, whether it is duplicated or not. It was an action packed week. Problem: You have given an array of objects, which could be an array of integers and or array of Strings or any object which implements the Comparable interface.