arraylist

问题 I'm doing some leetcode challenges related to backtracking, namely: https://leetcode.com/problems/permutations/ Where I need to return List<List<Integer>> as the type, however my List<List<Integer>> only gets populated correctly if I accept List<Integer> as my parameter and I cast it to ArrayList<Integer> while I add it in the main result. Code : List<List<Integer>> result = new ArrayList<>(); public List<List<Integer>> permute(int[] nums) { bt(new ArrayList<Integer>(), nums); return result;

问题 I'm creating an Android application. The problem is that when I press the button and pass the data to the new array, it goes to black and giving me this error: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.util.ArrayList.add (java.lang.Object) 'on a null object reference By debugging, it gives me something in the string: mExampleList.add(Ticket) My ExampleAdapter class: public class ExampleAdapter extends RecyclerView.Adapter<ExampleAdapter

问题 I'm creating an Android application. The problem is that when I press the button and pass the data to the new array, it goes to black and giving me this error: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.util.ArrayList.add (java.lang.Object) 'on a null object reference By debugging, it gives me something in the string: mExampleList.add(Ticket) My ExampleAdapter class: public class ExampleAdapter extends RecyclerView.Adapter<ExampleAdapter

问题 I'm creating an Android application. The problem is that when I press the button and pass the data to the new array, it goes to black and giving me this error: Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'boolean java.util.ArrayList.add (java.lang.Object) 'on a null object reference By debugging, it gives me something in the string: mExampleList.add(Ticket) My ExampleAdapter class: public class ExampleAdapter extends RecyclerView.Adapter<ExampleAdapter

问题 So I am working with Kotlin on this project, I mainly use Java so I'm trying to find equivalents in Kotlin to achieve the same functionality. I am getting a JSONArray from my Database and storing it in a Serializable data class called Congregation it has the following variables id: Int, name: String, language: String I now have a registration activity in which there is a "Congregation" input, I decided to make this an AutoCompleteTextView so that I could suggest possible values matching what

问题 This is my arraylist ArrayList<Courses> list = new ArrayList<Courses>(); list.add( new Courses(350,5/20/2020) ); list.add( new Courses(350,4/20/2019 ); list.add( new Courses(350,3/20/2018) ); list.add( new Courses(360,6/20/2020) ); list.add( new Courses(360,5/20/2019) ); list.add( new Courses(370,5/20/2020) ); list.add( new Courses(370,5/19/2018) ); list.add( new Courses(360,4/10/2016) ); public class Courses{ int coursenum; Date date; } How can I remove elements so that the arraylist

问题 This is my arraylist ArrayList<Courses> list = new ArrayList<Courses>(); list.add( new Courses(350,5/20/2020) ); list.add( new Courses(350,4/20/2019 ); list.add( new Courses(350,3/20/2018) ); list.add( new Courses(360,6/20/2020) ); list.add( new Courses(360,5/20/2019) ); list.add( new Courses(370,5/20/2020) ); list.add( new Courses(370,5/19/2018) ); list.add( new Courses(360,4/10/2016) ); public class Courses{ int coursenum; Date date; } How can I remove elements so that the arraylist

问题 so I am currently working on a project for school. My initial program ran fine and then I was told to refactor my array into an array list. Eclipse is highlighting one specific line with the error that 'The lefthand side of an assignment must be a variable' . Everything else in the program seems to have no other issues. I have tried a few different things to fix this problem and have hit a wall. I've attached a copy of the section of code causing me issue, and I hope this question isn't too

问题 Following is the structure of the document i have in a collection in MongoDB { "_id": { "$oid": "5f48e358d43721376c397f53" }, "heading": "this is heading", "tags": ["tag1","tag2","tag3"], "categories": ["projA", "projectA2"], "content": ["This", "is", "the", "content", "of", "the", "document"], "timestamp": 1598612312.506219, "lang": "en" } When i am importing data in PDI using the mongodb input step the system is putting each array of the "content" element in a different field I want to

问题 Following is the structure of the document i have in a collection in MongoDB { "_id": { "$oid": "5f48e358d43721376c397f53" }, "heading": "this is heading", "tags": ["tag1","tag2","tag3"], "categories": ["projA", "projectA2"], "content": ["This", "is", "the", "content", "of", "the", "document"], "timestamp": 1598612312.506219, "lang": "en" } When i am importing data in PDI using the mongodb input step the system is putting each array of the "content" element in a different field I want to