I am programming in java. Say I have an custom object Item I have list of Items. Now, What is best way in java to know, list of Items contain some Items with same value for itemNumber. Answer To search for a specific item with some item number: To get lists of items for all item numbers: You can use
Tag: arraylist
How to remove the brackets [ ] from ArrayList#toString()?
I have created an Array List in Java that looks something like this: When I print errors I get it errors as [1,2,3,4,5,6,7,8,9] Now I want to remove the brackets([ ]) from this array list. I thought I could use the method errors.remove(“[“), but then I discovered that it is just boolean and displa…
Declaring initial capaity for a list in java is a bad technique?
I have multiple ArrayLists with the same capacity. I fill these lists by reading a file. I know that one difference between an Array and an ArrayList is that the Array have a fixed capacity while the ArrayList have a variable capacity. You should explicitly specify the array length when you declare it, but th…
How to add an item only if no other items exist with the same name in the arraylist?
How would I go about only inserting an item if the item does not have the same name as the other items in the arraylist within my insertUniqueItem() method? Answer You need to check if an item with the same name already exists in your list:
Adding null values to arraylist
Can I add null values to an ArrayList even if it has a generic type parameter? Eg. If so, will return 1 or 0? If I can add null values to an ArrayList, can I loop through only the indexes that contain items like this? Or would the for each loop also loop through the null values in the list?
How to sort dates of type string in java
I am building a android project where am storing some details which includes date as string,but now I need to sort the list view by date.I am bit confused on how to do it.I am done with everything but need to sort the list by date. Here is the overview of how am storing data. I have an arraylist of
Duplication on ArrayList Java
my title is bad but I don’t have an idea what it should be. My question is simple, I have four arraylist and I want to get similar words from two of them and put another arraylists. Anyway my array lists like; I tried this; But as you see arrList1 and arrList2 have duplicates so arrList4 will have same …
Incompatible types List of List and ArrayList of ArrayList
The below line gives me error : What is the reason? EDIT I understand if I change my second ArrayList to List, it does not give me error. I want to know the reason of error though. Thanks Answer If you had a List<List<Integer>> then you’d be able to add a LinkedList<Integer> to it. But…
Getting values from one Array List using objects of another array list java
I have 3 ArrayLists. Students (ID, Name, Program) Courses (ID, Name, Credit Hours) StudentCourses (StudentId, CourseID) I am searching from StudentCourses by passing the StudentID and getting the courses registered with his/her name. My StudentCourse ArrayLIst has objects like this 49 (Student ID) CS233(Cours…
How do I remove duplicate objects from two separate ArrayLists?
Before beginning, I think that this question has a very simple answer that I’m just overlooking. I figured a few more eyes on the question at hand will be able to point out my problem fairly quickly. I have two ArrayLists that I want to compare and remove duplicates from each of them. The first ArrayLis…