Question

我在线程＆＃34; main＆＃34;中有一个＆＃34;异常。 java.lang.IllegalStateException：扫描程序已关闭＆＃34;我无法插上。

我几乎完成了这个应用程序（用Java编写）。它将int转换为二进制，反转二进制，并将反转的二进制转换为十进制。它运行，没有错误，但是当它终止时：

Exception in thread "main" java.lang.IllegalStateException: Scanner closed
at java.util.Scanner.ensureOpen(Unknown Source)
at java.util.Scanner.next(Unknown Source)
at intToBinary.AnotherOrCloseIntToBinary.enterAnotherInt(AnotherOrCloseIntToBinary.java:24)
at intToBinary.IntToBinary.useIntToBinary(IntToBinary.java:48)
at intToBinary.AnotherOrCloseIntToBinary.enterAnotherInt(AnotherOrCloseIntToBinary.java:29)
at intToBinary.IntToBinary.useIntToBinary(IntToBinary.java:48)
at intToBinary.AnotherOrCloseIntToBinary.enterAnotherInt(AnotherOrCloseIntToBinary.java:29)
at intToBinary.IntToBinary.useIntToBinary(IntToBinary.java:48)
at intToBinary.IntToBinary.main(IntToBinary.java:18)

欢迎任何有关应用程序任何部分的建议。这样做不到一年，所以我总是要学习。但主要是，我想解决上述问题。

感谢。

 <!-- language: lang-java -->

package intToBinary;

import java.util.Scanner;

public class IntToBinary 
{

    private static int invertedBinaryDecimal;
    private static int _n;
    private static String binaryString;
    private static String invertedBinaryString;

    static Scanner in = new Scanner(System.in);

    public static void main(String[] args) 
    {
        greeting();
        useIntToBinary();
    }

    public static void greeting()
    {
        System.out.println("*Int To Binary*");
    }

    public static void useIntToBinary()
    {
        System.out.println("Please enter an integer number: ");
        while ((!in.hasNextInt())) 
        {
            System.out.print("You did not enter an integer number.  An integer number(whole
            numbers or counting numbers) is a    number like: 1, 2, 3...");
            System.out.print("Please enter an integer number: ");
            in.nextInt();
        }

        _n = in.nextInt();

        getBinary();
        getInvertedBinary();
        getIntegerComplement();

        System.out.println("You entered integer number: " + _n );
        System.out.println("In binary(base 2): " + binaryString);
        System.out.println("The inversion of this binary(base 2): " + invertedBinaryString);
        System.out.println("The inverted binary(base 2) in decimal(base 10) is: " +
        invertedBinaryDecimal);
        AnotherOrCloseIntToBinary.enterAnotherInt();
    }

    public static void getBinary()
    {
        binaryString = Integer.toBinaryString(_n);          
    }

    public static void getInvertedBinary()
    {
        invertedBinaryString = binaryString.replaceAll("0", "x").replaceAll("1",
        "0").replaceAll("x", "1");
    }

    public static void getIntegerComplement()
    {
        invertedBinaryDecimal = Integer.parseInt(invertedBinaryString, 2);  
    }
}

＆＃13;

package intToBinary;

public class AnotherOrCloseIntToBinary 
{
	private static int state;
	private static String enterYOrN;
	
	 public static void enterAnotherInt() 
	 {
		 state = 0;
		 while (state < 2) 
		 {
			 switch (state) 
			 {
			 	case 0: 
			 		System.out.println();
			 		System.out.println("Do you want to enter another integer number? (y/n)");
			 		break;
		    	case 1:
		    		goodBye();
		    		break;
			 }
		          	 
			 enterYOrN = IntToBinary.in.next();
		    
			 if(enterYOrN.equalsIgnoreCase("y")) 
			 {
				 state = 0;
				 IntToBinary.useIntToBinary();
			 }
			 else if(enterYOrN.equalsIgnoreCase("n")) 
			 {
				 state++;
			 }	
		 }
	 }
	 
	 public static void goodBye()
	 {
	    	System.out.println("Thank you for using Int To Binary.");
	    	System.out.println("Good bye.");
	    	
	    	IntToBinary.in.close();
	 }
}

＆＃13;

Answer 1

您正试图从已关闭的扫描仪中读取：

         switch (state) 
         {
            case 0: 
                System.out.println();
                System.out.println("Do you want to enter another integer number? (y/n)");
                break;
            case 1:
                AnotherOrCloseIntToBinary.goodBye(); // here you close the scanner
                break;
         }

         enterYOrN = IntToBinary.in.next(); // here you try to read from a 
                                            // closed scanner

对goodBye()方法的调用可能只应位于main方法的最后一行。

Answer 2

您的代码存在两个问题。您已经确定的一个，它试图从已经关闭的Scanner中读取。在致电return之后立即enterAnotherInt()来解决AnotherOrCloseIntToBinary.goodBye()

     switch (state) 
     {
        case 0: 
            System.out.println();
            System.out.println("Do you want to enter another integer number? (y/n)");
            break;
        case 1:
            AnotherOrCloseIntToBinary.goodBye();
            return; // instead of break;
     }

您尚未意识到的第二个问题是in.nextInt()循环内的while来电。

    while ((!in.hasNextInt())) 
    {
        System.out.print("You did not enter an integer number.  An integer number(whole numbers or counting numbers) is a    number like: 1, 2, 3...");
        System.out.print("Please enter an integer number: ");
        in.nextInt(); // use in.next() here
    }

要查看失败的原因，只需在代码提示输入整数时输入非数字输入。您将收到InputMismatchException。它失败的原因是你已经在循环中，因为输入不是一个数字，但是你的代码继续前进并在扫描器上发出nextInt()调用，然后就会失败。

要解决此问题，只需使用in.next()代替nextInt()。

Java IntToBinary应用程序：线程中的异常＆＃34; main＆＃34; java.lang.IllegalStateException：扫描程序已关闭

2 个答案: