java.util.scanner

问题 I am trying to get text input from the keyboard in Java 6. I am new to the language and whenever i run the following code, I get this error: package test1; import java.util.Scanner; public class Test { public static void main(String[] args) { boolean quit = false; while (!quit){ Scanner keyIn; String c = "x"; while (c != "y" && c != "n") { keyIn = new Scanner(System.in); c = keyIn.next(); keyIn.close(); } if (c == "n") quit = true; } } } Exception in thread "main" java.util

问题 I was solving a competitive problem and in problem, I was taking user input using scanner. These are 2 code segments, one closing scanner and one without closing scanner. Closing scanner import java.util.Scanner; public class JImSelection { public static void main(String[] args) { Scanner scanner = new Scanner(System.in); int n = Integer.valueOf(scanner.nextLine()); while (n-- > 0) { double number = (Math.log(Long.valueOf(scanner.nextLine())) / Math.log(2)); System.out.println((int) number -

问题 I have a question regarding data validation and scanners.The following piece of code checks userinput.Anything other than an integer is not allowed and the user is asked to re-enter a value.My question is that the code works only if the scanner is declared within the while loop.The program executes infinitely if the scanner is declared outside.Why is that?Thanks. int UserInp; boolean dataType=false; while(dataType==false) { Scanner sc=new Scanner(System.in); try { System.out.print("\nEnter a

问题 Here's my code: import java.util.Scanner; class Graph{ boolean [][]array; int N; Graph (){ array = new boolean [1001][1001]; N=0; } void read_graph() { Scanner sc = new Scanner(System.in); N = sc.nextInt(); sc.nextLine(); String str; String []substr; for (int K=1; K<=N; K++){ str = sc.nextLine(); substr = str.split(" "); for (int I=0; I<substr.length; I++) System.out.println(substr[0]+" "+substr[I]); } } void query(){ Scanner sc = new Scanner(System.in); int P, Q; int counter = 0; boolean

问题 I would like to know about other ways of getting input from users using other classes like BufferedReader ,etc rather than using Scanner class. So, was there any other way of getting input from the user? If so, was it efficient than Scanner class? 回答1: if you are using the Java SE6 or higher then you can make use of Console clas Console console = System.console(); if (console==null){ System.out.print("console not available "); }else { String line = console.readLine("Enter name :"); System.out

问题 I have two blocks of code here. One scanner properly waits user input, and the other just blows right through it and calls nextInt() which returns a NoSuchElementException . Here is the block that works: public void startGame() { out.println("Player1: 1 for dumb player, 2 for smart player, 3 for human player."); Scanner scan = new Scanner(System.in); p = scan.nextInt(); if (p == 1) p1 = new DumbPlayer("ONE"); if (p == 2) p1 = new SmartPlayer("ONE"); else p1 = new HumanPlayer("ONE"); out

问题 I am trying to solve the following question: https://www.hackerrank.com/challenges/sherlock-and-anagrams This is my code import java.util.*; public class Solution { public static boolean check(String s1,String s2) { int [] count1 = new int[26]; for( int i = 0; i < s1.length(); i++ ) { char ch1 = s1.charAt(i); count1[ch1-'a']++; } int [] count2 = new int[26]; for( int i = 0; i < s2.length(); i++ ) { char ch2 = s2.charAt(i); count2[ch2-'a']++; } int count =0; for(int j=0;j<26;j++) { count =

问题 How do I read input line by line in Java? I searched and so far I have this: import java.util.Scanner; public class MatrixReader { public static void main(String[] args) { Scanner input = new Scanner(System.in); while (input.hasNext()) { System.out.print(input.nextLine()); } } The problem with this is that it doesn't read the last line. So if I input 10 5 4 20 11 6 55 3 9 33 27 16 its output will only be 10 5 4 20 11 6 55 3 回答1: Ideally you should add a final println() because by default

问题 I'm programming a game and in the program I need to add new enemies based off of a file. Right now my problem is that I've run into an infinite while loop when trying to read this file. I'm relatively new to programming so I'm not exactly sure how to fix this. Here is the problem code. An example of how the entry in the file looks is: "Troll,6,4,1". Thank you for your help. try { Scanner input = new Scanner(new File(filename)); while(input.hasNext()); { input.useDelimiter(",|\n"); String name

问题 I am trying to edit a matlabfile and replace some of the coding parts init in some specific lines. However, using the format below to make the changes it wont change the line context at all. (it will print the same old line). Any idea what am I doing wrong? 'replaceAll' is not suitable to replace some words with some others in the lines? Thanks in advance. try { PrintWriter out = new PrintWriter(new FileWriter(filenew, true)); Scanner scanner = new Scanner(file); while (scanner.hasNextLine())