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Checking Console.ReadLine()!=null

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问题 i am making a CMD for my applcation, and figure i have a trouble when i check Console.ReadLine!=null ---Full Code--- string input = Console.ReadLine(); if(input!=null) { SomeFunction(input); } ---End Of Code--- in SomeFunction() i split this string, so for example: Console.WriteLine(input[0]); so Problem is: It works if user hits enter once. But if use does that again i am getting an exception: That [0] does not exist. 回答1: When you hit ENTER , Console.ReadLine returns empty string . It doesn

JSF login filter, session is null

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问题 I've been trying to follow this answer primarily but I always get redirected to my login.xhtml (except for when i log in from the login page) because this... AppManager am = (AppManager) req.getSession().getAttribute("appManager"); Is always null. I've been trying to print out user info on the login screen and no matter how i get there all fields(username, password, loggedIn...) are always null, even if i type the adress straight from the admin page (that's where you get when you log in). How

Printing Null Character (“\x00”) in Python vs C

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问题 When I code and run the statement: print "\x00\x00\x00" in Python it outputs three blank spaces followed by a newline. But in C, when I code and run the statement: char hex[] = "\x00\x00\x00"; printf("%s\n", hex); it interprets the NULL bytes like I thought it would: it doesn't do anything. So why in Python are NULL bytes treated as spaces?... 回答1: So why in Python are NULL bytes treated as spaces? It's not. Your terminal/console is treating them like spaces. C just happens to stop at the

Can a java subclass's private final field be initialized before the super constructor completes?

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问题 I have a pair of classes looking like this; public abstract class Class1 { //... public Class1() { //... function2(); //... } protected abstract void function2(); } public class Class2 implements Class1 { private final OnSomethingListener mOnSomethingListener = new OnSomethingListener() { @Override onSomething() { doThatOtherThing(); } } protected void function2() { //uses mOnSomethingListener //however mOnSomethingListener is null when this function is called from super() //... } public

Webbrowser control's window.external is ALWAYS null

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问题 The Web browser's Window.External object is always null! To reproduce drop a web browser on a new winform and type: Option Strict Off Public Class Form1 Private Sub Form1_Load() Handles MyBase.LoadMe.WebBrowser1.Document.Window.DomWindow.External.AddFavorite("http://www.google.com") End Sub End Class Make certain you go to the Assembly Information dialog and check "Make Assembly COM-Visible." This is necessary. I am lost as to why with a COM visible assembly the External object is always

How to exit the program when Ctrl+D is entered in Java?

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问题 Below is a section of my Reverse Polish Calculator. If an integer is entered, push it to the stack and, if = is pressed, peek the result. However, I want to add another condition: if CTRL + D is pressed by the user, the program exits. I've had a look online but can't seem to find any solutions. Any ideas? Thanks. Scanner mySc = new Scanner(System.in); //If input is an integer, push onto stack. if (mySc.hasNextInt()) { myStack.push(mySc.nextInt()); } //Else if the input is an operator or an

How to convert min to hours in swift3?

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问题 This is my JSON data { "service_facility_id": 1, "service_id": 4, "facility_name": "Fitting", "charge_per_min": 40, "charge_per_km": 50 }, { "service_facility_id": 10, "service_id": 4, "facility_name": "Health Care", "charge_per_min": 100, "charge_per_km": 0 } Currently i'm using Get method to print specific JSON output in X Code. So i managed to Minute( charge_per_min ) value . But I want to display in a label in HH(Hours) format, so how to convert it minute to hours formate and disply into

mysql - “column cannot be null”

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问题 as you see in the title, even if i removed "not null" feature from the related field, it still doesn't let me to insert null value for that field although the field is nullable! Any help would be appreciated. EDITED Create: CREATE TABLE `review` ( .. `RATING` int(11) DEFAULT NULL, .. (`CATALOG_ID`) ) ENGINE=InnoDB AUTO_INCREMENT=31625 DEFAULT CHARSET=latin5 ROW_FORMAT=DYNAMIC Query: INSERT INTO review (RATING,..) VALUES (null,..); Error message: Error: Column 'RATING' cannot be null SQLState:

线性表之单链表

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#include<iostream> using namespace std; /* 有一个头节点下标都是从0开始头节点的下表是0，所以元素的下标是从1开始，添加删除都是以1为下标的位置头节点的value代表链表长度 */ struct LinkNode { int value; LinkNode* next; }; LinkNode* createLinkList() { LinkNode* head = (LinkNode*)malloc(sizeof(LinkNode)); head->next=NULL; head->value=0; return head; } bool insertElem(int pos,int value,LinkNode* head) { if(pos<=0)return 0; LinkNode* p = head; int j=0; while(p!=NULL && j<pos-1)//定位到pos-1的元素，也就是待插入元素的前一个元素 { p=p->next; j++; } if(p!=NULL)//限制插入元素的位置是【1,链表长度+1】这个闭区间 { //因此这里辅助指针的位置【0，链表长度】这个闭区间 LinkNode* newNode = (LinkNode*)malloc(sizeof(LinkNode));

null == foo versus foo == null [duplicate]

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问题 This question already has answers here : Which is more effective: if (null == variable) or if (variable == null)? [duplicate] (9 answers) Closed 6 years ago . This may just be a style question, but I'm reading a Java coding book ('Programming Android') and the writer all declares null first before a variable method, a practice I am not familiar with. For example: if (null == foo) { //code here } or if (null != foo) { //code here } instead of if (foo == null) { //code here } I can't see how