扫描仪类InputMismatchException和警告 [英] Scanner Class InputMismatchException and Warnings

问题描述

我在运行该程序时遇到麻烦.该程序采用诸如"A = 7"之类的表达式，并将变量A(字符串)和数字7放入Map容器​​中.如果不是我正确解析了导致错误或其他原因的字符串，我就不是.

I am having trouble running this program. The program takes an expression such as "A = 7" and puts the variable A (String) and the number 7 in a Map container. I'm not if i'm not parsing the string correctly which is causing the error or for some other reason.

    Exception in thread "main" java.util.InputMismatchException
    at java.util.Scanner.throwFor(Scanner.java:909)
    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 Commander.main(Commander.java:21)

此外，我收到以下警告消息，它实际上是第一个

Furthermore, I get the following warning message which is actually a first

Note: Commander.java uses unchecked or unsafe operations.
Note: Recompile with -Xlint:unchecked for details.

代码

import java.util.Scanner;
import java.util.Map;
import java.util.HashMap;

public class Commander
{
    public static void main(String[] args)
    {
        Map<String,Integer> expression = new HashMap();

        Scanner sc = new Scanner(System.in);

        String Variable , assignmentOperator;
        int Value;

        while(sc.hasNextLine())
       {

            Variable = sc.nextLine();
            assignmentOperator = sc.nextLine();
            Value = Integer.parseInt(sc.nextInt());

            expression.put(Variable,Value);

            for(String key: expression.keySet())
                System.out.println(key + " - " + expression.get(key));
        }
    }
}

推荐答案

，您将获得Commander.java使用未经检查或不安全的操作.因为您在HashMap之后缺少<>.

you get Commander.java uses unchecked or unsafe operations. because you are missing <> after HashMap.

Map<String,Integer> expression = new HashMap<>();

如果下一个标记与有效的Integer正则表达式不匹配或超出范围，则sc.nextInt()可能导致

和InputMismatchException.这是更新的代码.

and InputMismatchException can be caused by sc.nextInt() if the next token doesn't match the valid Integer regex or is out of range. Here is updated code.

import java.util.Scanner;
import java.util.Map;
import java.util.HashMap;

public class Commander
{
    public static void main(String[] args)
    {
        Map<String,Integer> expression = new HashMap<>();

        Scanner sc = new Scanner(System.in);

        String Variable , assignmentOperator;
        int Value;

        while(sc.hasNextLine())
       {

            Variable = sc.nextLine();
            assignmentOperator = sc.nextLine();
            Value = Integer.parseInt(String.valueOf(sc.nextInt()));

            expression.put(Variable,Value);

            for(String key: expression.keySet())
                System.out.println(key + " - " + expression.get(key));
        }
    }
}

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