無法使該Java程序正常工作

Question

好的，稍微更改了代碼，但是程序仍然無法正常運行。 我希望能夠在程序運行時在Java控制台中輸入產品類型（水果），輸入任何類型的水果（香蕉，蘋果或橙子），然后輸入數量。

import java.util.*;

public class demo {

public static void main(String[] args) {

    Scanner sc = new Scanner(System.in);

    String str[] = { "Bananas", "Apples", "Oranges" };
    double price[] = { 2.09, 2.59, 2.25 };
    int i = 0;
    int j = 0;

    System.out.print("Enter type of product: ");
    String string = sc.nextLine();
    if ("fruit".equals(string)) {
        while (i < str.length) {
            while (j < price.length) {
                System.out.print(str[i++] + ": " + "£" + (price[j++]) + "p per bag \n");

            }
        }
    }
    System.out.print("\n");
    System.out.print("Enter which type of " + string + ": ");

    String string1 = sc.nextLine();

    boolean strs = "bananas".equals(string1);
    boolean strs1 = "apples".equals(string1);
    boolean strs2 = "oranges".equals(string1);
    if (strs) {
        System.out.print("Enter qty of " + str[0] + " (by bag): ");
    }

    if (strs1) {
        System.out.print("Enter qty of " + str[1] + " (by bag): ");

    }
    if (strs2) {
        System.out.print("Enter qty of " + str[2] + " (by bag): ");
    }

    int qty = sc.nextInt();
    int[] a = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
    int h = 1;
    if ((a[h] == (qty)) && (strs) || (strs1) || (strs2)){
        System.out.print("\n");
        System.out.print(qty + " bag(s) of " + string1 + " have been added to your basket, " + "total costing £"
                + (qty) * price[0] + "p");

        }
    }   
}

還有其他想法嗎？

Answer 1

錯誤發生在String string = sc.next（“ fruit”）; 可以將其更改為sc.nextLine（）或類似下面的內容

public static void main(String[] args) {

Scanner sc = new Scanner(System.in);

String str[] = { "Bananas", "Apples", "Oranges" };
double stk[] = { 1.09, 1.59, 1.25 };
int i = 0;
int j =0;

try {
    System.out.print("Enter type of product: ");
    String string = sc.next();

    while (i < str.length) {
        while (j < stk.length) {
        System.out.print(str[i++] + ": " + "£" + (stk[j++]) + "p per bag \n");

        }
    }
    System.out.print("\n");
    System.out.print("Enter which type of "+string+": ");
    String string1 = sc.next();
    if(string1 != null) {
        System.out.print("Enter qty of "+string1+ "(per bag) \n");
    } 
    String string2 = sc.next();     
    if(string2 != null) {
            System.out.print("Enter qty of " +string2+ "(in lbs) \n");

    } 
    String string3 = sc.next();
    if (string3 != null) {
            System.out.print("Enter qty of " +string3+ "(in lbs) \n");

    }

} catch (Exception e) {
    System.out.println("Eror");
    e.printStackTrace();
    }
}

Answer 2

您有錯誤是正在讀取字符串。

更換

String string = sc.next("fruit");          // Line 17
String string1 = sc.next("bananas");       // Line 26
String string2 = sc.next("apples");        // Line 30
String string3 = sc.next("oranges");       // Line 35

同

String string = sc.nextLine();             // Line 17
String string1 = sc.nextLine();            // Line 26
String string2 = sc.nextLine();            // Line 30
String string3 = sc.nextLine();            // Line 35

如果要檢查輸入的String ，請使用以下代碼：-

if(string.equals("fruit")){ 
   // statements
}

Answer 3

根據JavaDoc，您得到的InputMismatchException是

由Scanner拋出，以指示檢索到的令牌與預期類型的​​模式不匹配，或者令牌超出預期類型的​​范圍。

因此，如果您沒有按要求編寫"fruit" （ String string = sc.next("fruit") ），則執行將以該異常終止。 因此， 要修復您的代碼，您應該替換

String string = sc.next("fruit");

用類似的東西

String string = sc.nextLine();
if ("fruit".equalsIgnoreCase(string)) { /* design your control flow as you want */

您可以將相同的規則應用於代碼中存在的其他sc.next() 。

旁注： 切勿將異常吞入catch塊； 始終記錄它們。

Answer 4

輸入行掃描錯誤。要使用Java掃描輸入數據，請使用

Scanner in = new Scanner(System.in);
int a = in.nextInt(); // To input integer
char ch = in.nextChar(); // To input character
String str = in.nextLine(); // To get a complete line of input
String s = in.next(); //To get a single string

根據以上給出的內容替換您的輸入行。

干杯:)