arraylist

问题 Lets say I have an ArrayList of a object User so ArrayList<user> . A User object has a property userID . Rather than iterating the list myself and adding userIDs to a separate list, is there and API call where I could pass it the property I want on that object and have a list of these properties returned to me? Had a look through the API and nothing stood out. Looking for a solution in Java 7 or <. 回答1: You can do this using lambdas expressions (Java 8) : import java.util.*; import java.util

问题 I'm very curious about how this thing works inside Android. I have a class with two List<> inside, instantiated at runtime and loaded with objects created while reading some data, I want to know what happens with those Lists in this situation: Class A has List B and List C with many other initialized objects inside. Another different class get a reference of List C from a method of Class A, like public List<myObject> GetList() . Somewhere in code, Class A is no longer used and application

问题 Sample List ArrayList<MyObject> list = new ArrayList<MyObject>(); list.add(new MyObject (1, "2011-04-27T09:40:01.607")); list.add(new MyObject (1, "2011-05-27T09:42:01.607")); list.add(new MyObject (2, "2011-06-27T09:42:01.607")); list.add(new MyObject (5, "2011-07-27T09:43:01.607")); list.add(new MyObject (6, "2011-08-27T09:44:01.607")); list.add(new MyObject (6, "2011-09-27T09:45:01.607")); list.add(new MyObject (1, "2011-10-27T09:46:01.607")); 1:-How to Sort ArrayList with the respect of

问题 This is what I want: As you can see in the image I have stored sub-Lists on each main List position. Now I want to display one item from sub-list when main loop is working. If looping counter is greater than sub-List size then it starts again from 0 and increments one by one. What I have done: I have got the data from database and stored sub-Lists in a ArrayList public static ArrayList<ArrayList<HashMap<String, String>>> selectdataloop(SQLiteDatabase db, String TableName,String userfield

问题 I am dealing with problem to implement groovy lambda function getting text from List collection into List collection. The original java code: list.stream().map(WebElement::getText).collect(Collectors.toList()); My Groovy version fails: list.stream().map({ WebElement } as String).collect(Collectors.toList()) groovy.lang.MissingMethodException: No signature of method: java.util.stream.ReferencePipeline$Head.map() is applicable for argument types: (java.lang.String) values: [quality1

问题 I am using Map<Integer, String> adi = new HashMap<Integer, String>(); for(int u=0; u< sari_nodes.size();u++){ adi.put(u, sari_nodes.get(u)); } for (Map.Entry<Integer, String> entry : adi.entrySet()) { tv.setText(tv.getText()+"Key : " + entry.getKey()+ " Value : " + entry.getValue()+"\n"); } My output is : key: 0 Value : cat key: 1 Value : dog key: 2 Value : car key: 3 Value : car key: 4 Value : car key: 5 Value : car I want to repeat the key for same entry so that my output looks like key: 0

问题 I seem to be having trouble initializing another textview in my expandablelist. I already have one, but I'm trying to add a second one in the same child. I made a new setter and getter for the textview(ltv),and I keep getting java.lang.ArrayIndexOutOfBoundsException: length=0; index=0 error in my logcat whenever I try to initialize it with my other one. Please see my code below, what am I missing? EDIT: size is 5 and I have 20 elements per array for an example. MainActivity: public class

问题 //I have retrieved a Result from MySQL and created and Array-list User .i have sent this //US er Array-list in and sent it through request Response Object. Now i need to display iton //s JSP page. //1.Without JSTL //2.With JSTL //The Name of table is user_reg it has four fields id,username,password,email. //please do explain with example. i need to dispay all fields in a jsp page. but i dont want //to do the jdbc work on the JSP package kinder.dto; public class User { private String id;

问题 I've been searching for a simple example of this with no luck. In my android application I have two activities: 1. The main activity which is launched at startup 2. A second activity which is launched by pressing a button on the main activty. When the second activity is finished (by pressing a button) I want it to send back an ArrayList of type MyObject to the main activity and close itself, which the main activity can then do whatever with it. How would I go about achieving this? I have been

问题 I have an ArrayList of doubles, and i need to find the average between all numbers. The amount of Double instances in the arraylist is not constant, could be 2, could be 90 I have been trying for hours to get the algorithm myself but could not get it to work in anyway. do you have any advice? or maybe you can link me to an existing library to get this average? Thank you 回答1: Create a sum variable: double sum = 0; Go through the elements in the list using a for-loop: for (double d : yourList)