线程“主”java.util.NoSuchElementException 中的异常 - 扫描仪

Question

当扫描仪在（while 循环）主打印异常中搜索时间时：

Exception in thread "main" java.util.NoSuchElementException
	at java.util.Scanner.throwFor(Scanner.java:907)
	at java.util.Scanner.next(Scanner.java:1530)
	at java.util.Scanner.nextInt(Scanner.java:2160)
	at java.util.Scanner.nextInt(Scanner.java:2119)
	at eg.edu.alexu.csd.ds.linkedList.cs49.Polynomial.main(Polynomial.java:17)

在调试代码中失败标志 = function.swit(new Scanner(System.in).nextInt()); 这是代码：

public class Polynomial {
	SinglyLinkedList A = new SinglyLinkedList();
	SinglyLinkedList B = new SinglyLinkedList();
	SinglyLinkedList C = new SinglyLinkedList();
	SinglyLinkedList R = new SinglyLinkedList();
	
	public static void main(String[] args)throws Exception{
		Polynomial function = new Polynomial();
		boolean flag = true;
		while(flag){
			function.menu();
			flag = function.swit(new Scanner(System.in).nextInt());
		}
	}
	public boolean swit(int choose){
		Polynomial function = new Polynomial();
		boolean flag = true;
		switch(choose){
	    	case 1: function.setSwitch();break;
	    	case 2: function.printSwitch();break;
	    	case 3: function.addSwitch();break;
	    	case 4: function.subtractSwitch();break;
	    	case 5: function.multiplySwitch();break;
	    	case 6: function.evaluateSwitch();break;
	    	case 7: function.clearSwitch();break;
	    	default : flag = false;
	    }
		return flag;
	}

Answer 1

在执行nextInt()之前检查元素是否存在hasNextInt()

应该是这样的

Scanner scanner = new Scanner(System.in);
int value = 0;
if(scanner.hasNextInt()) {
  value = scanner.nextInt(); 
}
flag = function.swit(value);