如何使用Scanner java重复读取用户输入

我正在尝试为我的程序创建一个简单的菜单来读取用户输入。 这是代码：

public void menu() { String command; System.out.println("To operate with words write: a"); System.out.println("To operate with products write: b"); System.out.print("\nGive the command: "); Scanner scanner = new Scanner(System.in); command = scanner.nextLine(); if (command.equals("a")) { System.out.println("\nGood job! You have chosen the word program\n"); System.out.println("You can only use the following commands: "); System.out.println("exit - to exit the program"); System.out.println("add - to add a word into the map"); System.out.println("lookup - to lookup a word into the map\n"); System.out.print("Give a command: "); command = scanner.next(); while(scanner.hasNext()){ command = scanner.next(); if(command.equals("add")){ this.addWord(); } System.out.print("Give a command: "); command = scanner.next(); //Here I get the ERROR that throws Exception } } scanner.close(); } public static void main(String [] args) { HashTableInterface table = new HashTable(); Dictionary d = new Dictionary(table); RepositoryInterface repo = new Repository(d); ControllerInterface controller = new Controller(repo); Console c = new Console(controller); c.menu() } 

这是一个测试，我得到的例外：

 To operate with words write: a To operate with products write: b Give the command: a Good job! You have chosen the word program You can only use the following commands: exit - to exit the program add - to add a word into the map lookup - to lookup a word into the map Give a command: add add Give the word: mar Give the word's plural: mere The hash code for mar is: 3 Give a command: Exception in thread "main" java.util.NoSuchElementException at java.util.Scanner.throwFor(Scanner.java:907) at java.util.Scanner.next(Scanner.java:1416) at console.Console.menu(Console.java:56) at test.Prog.main(Prog.java:26) 

我从while循环中删除了第二个command = scanner.next（）但是它让我只读取一次用户输入。 怎么解决这个？

更新：AddWord方法：

 public void addWord() { Scanner scanner = new Scanner(new InputStreamReader(System.in)); System.out.print("Give the word: "); String word = scanner.nextLine(); System.out.print("Give the word's plural: "); String plural = scanner.nextLine(); scanner.close(); controller.addTheWord(word, plural); } 

Answer 1

您可以使用

 InputStreamReader str= new InputStreamReader (System.in); BufferedReader uinp= new BufferedReader (str); String val; val= uinp.readLine(); while (!".".equals(val)) { //do your stuff //..and after done, read the next line of the user input. val= uinp.readLine(); } 

Answer 2

你应该在while循环中使用switch case while不是if 。 开关盒应根据用户提供的输入提供function。

Answer 3

为什么不这样做：

 public class test { private static Scanner scanner; public static void main(String args[]) { scanner = new Scanner(System.in); printmenu(); getinput(); } private static void printmenu(){ System.out.println("To operate with words write: a"); System.out.println("To operate with products write: b"); } private static void getinput(){ System.out.print("\nGive the command: "); String command = ""; while (!scanner.hasNext()) { } command = scanner.next(); if (command.equals("a")) { System.out.println("\nGood job! You have chosen the word program\n"); System.out.println("You can only use the following commands: "); System.out.println("exit - to exit the program"); System.out.println("add - to add a word into the map"); System.out.println("lookup - to lookup a word into the map\n"); System.out.print("Give a command: "); while(scanner.hasNext()){ command = scanner.next(); if(command.contains("add")){ addWord(); } else{ System.out.println(command); } getinput(); } } else{ scanner.close(); } } public static void addWord() { System.out.print("Give the word: "); String word = scanner.next(); System.out.print("Give the word's plural: "); String plural = scanner.next(); //controller.addTheWord(word, plural); } 

}