Question

这是为了找到矩形的周长，面积和对角线度量。

这是我的代码：

public class Exer1Sano_an{
public static void main(String[] args) {
    Scanner kbd = new Scanner(System.in);

    String L,W;
    int L2,W2;
    String x;
    int x2;

    choice(x);
    measureW(W);
    measureL(L);

    x2=Integer.parseInt(x);
    L2=Integer.parseInt(L);
    W2= Integer.parseInt(W);
    processing();


     System.exit(0);
    }// end of main meathod


    // for length and width
    public static String measureW(String W){
        W=JOptionPane.showInputDialog("Enter the Width: ");
        return W;
    }
    public static String measureL(String L){
        L=JOptionPane.showInputDialog("Enter the Length: ");
        return L;

    }

    // for chioce
    public static String choice(String x){
        x=JOptionPane.showInputDialog("n\1. Perimiter of a Rectangle n\2. Area of        Rectangle n\3. Measurement of the Diagonals of a Rectangle");
        return x;
    }

    // for computation and printing
    public static void processing(){
        int areaRect;
        int periRect;
        double diagNal;         
        int L2,W2;          
        int x2;         

            if (x2==1)
                periRect=(2*L2)+(2*W2);
                JOptionPane.showMessageDialog(null, "The perimiter of your     rectanlge is" + periRect);

            if (x2==2)
                areaRect=L2*W2;
                JOptionPane.showMessageDialog(null, "The area of your rectanlge is" + areaRect);

            if (x2==3)
                diagNal=Math.sqrt((L2*L2)+(W2*W2));
                JOptionPane.showMessageDialog(null, "The measurement of the diagonals of your recangle is" + diagNal);          

    }

}// end of class

有人能帮帮我吗？它说我没有声明变量......但我已经有了。

Answer 1

在初始化之前，无法访问方法范围的变量引用。

这可能是你得到的编译错误。

例如，在致电choice(x)之前，必须为x显式指定一个值，event为String的默认值（null）。

Answer 2

将其更改为

import javax.swing.JOptionPane;

    public class Exer1Sano_an {
        public static void main(String[] args) {
            String L = null, W = null;
            String x = null;
            choice(x);
            measureW(W);
            measureL(L);

            processing();

            System.exit(0);
        }// end of main meathod

        // for length and width
        public static String measureW(String W) {
            W = JOptionPane.showInputDialog("Enter the Width: ");
            return W;
        }

        public static String measureL(String L) {
            L = JOptionPane.showInputDialog("Enter the Length: ");
            return L;

        }

        // for chioce
        public static String choice(String x) {
            x = JOptionPane
                    .showInputDialog("n\1. Perimiter of a Rectangle n\2. Area of        Rectangle n\3. Measurement of the Diagonals of a Rectangle");
            return x;
        }

        // for computation and printing
        public static void processing() {
            int areaRect = 0;
            int periRect = 0;
            double diagNal = 0;
            int L2 = 0, W2 = 0;
            int x2 = 0;

            if (x2 == 1)
                periRect = (2 * L2) + (2 * W2);
            JOptionPane.showMessageDialog(null,
                    "The perimiter of your     rectanlge is" + periRect);

            if (x2 == 2)
                areaRect = L2 * W2;
            JOptionPane.showMessageDialog(null, "The area of your rectanlge is"
                    + areaRect);

            if (x2 == 3)
                diagNal = Math.sqrt((L2 * L2) + (W2 * W2));
            JOptionPane.showMessageDialog(null,
                    "The measurement of the diagonals of your recangle is"
                            + diagNal);

        }

    }// end of class

Answer 3

您不需要在processing（）函数中再次声明x2，L2，W2。将它们移出main并使它们成为类变量。

未声明的变量错误

3 个答案: