Question

这是驱动程序类。问题出在开关上，直到我输入带字母的长度/宽度值来测试它是否捕获到异常，它都能正常工作，它将捕获该异常，但是从那一点开始，它将不允许您输入新的长度/宽度值每次我输入新的长度/宽度值时，它只会显示“输入介于0.0-20.0之间的长度值：请输入介于0.0-20.0之间的数字”

package week.pkg6.assignment.assignment.pkg7;

import java.util.*;

public class TestRectangle {

public static void main(String[] args)throws Exception
{        
    Scanner input = new Scanner( System.in );

    Rectangle TestRectangle = new Rectangle();

    int choice = getMenuChoice();       
    //week6assignment:Exercise 8.4 (TestRectangle)

    while ( choice != 3 )
    { 
        switch ( choice )
        {
        case 1:        
        try{
        //prompt user to enter a length value between 0.0 - 20.0                   
        System.out.print( "Enter length value between 0.0 - 20.0: " );
        //user enters a length value             
        TestRectangle.setLength( input.nextDouble());        
        }catch(Exception e)
        {System.out.println("Please enter a number between 0.0-20.0:");}            
        break;

        case 2:               
        try{
        //prompt user to enter a width value between 0.0 - 20.0                  
        System.out.print ( "Enter width value between 0.0 - 20.0: " );
        //user enters a width value                    
        TestRectangle.setWidth( input.nextDouble());  
        }catch(Exception e)
        {System.out.println("Please enter a number between 0.0-20.0:");}
        break;                                 
        } // end switch

    System.out.println ( TestRectangle.toString() );
    System.out.println();
    choice = getMenuChoice();
    }// end while
 } // end main

private static int getMenuChoice()throws Exception {

Scanner input = new Scanner( System.in );

System.out.println( "1. Set Length" );
System.out.println( "2. Set Width" );
System.out.println( "3. Exit" );
System.out.print( "Choice: " );
try{
return input.nextInt();
}catch(Exception e){System.out.println("Please enter 1, 2, or 3");}      
    return 0;
}//end method getMenuChoice
}//end clss

这是上述课程所驾驶的课程

package week.pkg6.assignment.assignment.pkg7;

public class Rectangle
{
private double length; // the length of the rectangle
private double width; // the width of the rectangle

public Rectangle()
{
setLength( 1.0f );
setWidth( 1.0f );
} // end Rectangle no-argument constructor

// constructor with length and width supplied
public Rectangle( double theLength, double theWidth ){
setLength( theLength );
setWidth( theWidth );
} // end Rectangle two-argument constructor

// validate and set length
public void setLength( double theLength )
{   
length = ( theLength >= 0.0 && theLength <= 20.0 ? theLength : 1.0f );
}// end method setLength

// validate and set width
public void setWidth( double theWidth ){
width = ( theWidth >= 0.0 && theWidth <= 20.0 ? theWidth : 1.0f );  
} // end method setWidth

// get value of length
public double getLength()
{
return length;
} // end method getLength

// get value of width
public double getWidth()
{
return width;

} // end method getWidth

// calculate rectangle's perimeter
public double perimeter()
{
return 2 * length + 2 * width;
} // end method perimeter

// calculate rectangle's area
public double area()
{
return length * width;
} // end method area

public String toString()
{
return String.format( "%s: %f\n%s: %f\n%s: %f\n%s: %f",
"Length", length, "Width", width,
"Perimeter", perimeter(), "Area", area() );
}//end method string
}//end class

Answer 1

删除此行：

Scanner input = new Scanner( System.in );

也来自getMenuChoice()和main()的

并放在类级别，因此您在整个代码中仅使用1个Scanner对象。
同时存在多个打开的Scanner对象可能是问题的根源。

如何在交换机内部使用try-catch？

1 个答案: