Update

src/finalexam/Database/ProductModificationAndDeletion.java

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+package finalexam.Database;
+
+import java.sql.Connection;
+import java.sql.DriverManager;
+import java.sql.PreparedStatement;
+import java.sql.ResultSet;
+import java.util.Scanner;
+
+public class ProductModificationAndDeletion {
+    private static final String DBDRIVER = "com.mysql.cj.jdbc.Driver";
+    private static final String DBURL = "jdbc:mysql://localhost:3306/xiaoshou?useUnicode=true&characterEncoding=utf-8&useSSL=false&serverTimezone=GMT";
+
+    public static void main(String[] args) throws Exception {
+        Class.forName(DBDRIVER);
+        Connection conn = DriverManager.getConnection(DBURL);
+        PreparedStatement pstmt = null;
+        ResultSet rs = null;
+        Scanner sc = new Scanner(System.in);
+        int choice;
+        do {
+            System.out.println("====超市商品管理维护====");
+            System.out.println("1、删除商品");
+            System.out.println("2、修改商品");
+            System.out.println("3、退出");
+            System.out.print("请选择（1-3）：");
+            choice = sc.nextInt();
+            switch (choice) {
+                case 1:
+                    System.out.print("输入商品编码：");
+                    String codeToDelete = sc.next();
+                    pstmt = conn.prepareStatement("SELECT * FROM t_shangping WHERE tiaoma = ?");
+                    pstmt.setString(1, codeToDelete);
+                    rs = pstmt.executeQuery();
+                    if (!rs.next()) {
+                        System.out.println("你输入的编码不存在，请重新输入");
+                    } else {
+                        pstmt = conn.prepareStatement("DELETE FROM t_shangping WHERE tiaoma = ?");
+                        pstmt.setString(1, codeToDelete);
+                        pstmt.executeUpdate();
+                        System.out.println("你成功删除该商品");
+                    }
+                    break;
+                case 2:
+                    System.out.print("输入商品编码：");
+                    String codeToModify = sc.next();
+                    pstmt = conn.prepareStatement("SELECT * FROM t_shangping WHERE tiaoma = ?");
+                    pstmt.setString(1, codeToModify);
+                    rs = pstmt.executeQuery();
+                    if (!rs.next()) {
+                        System.out.println("你输入的编码不存在，请重新输入");
+                    } else {
+                        System.out.print("商品名称（" + rs.getString("mingcheng") + "）：");
+                        String name = sc.nextLine();
+                        sc.nextLine();
+                        System.out.print("商品单价（" + rs.getDouble("danjia") + "）：");
+                        double price = sc.nextDouble();
+                        sc.nextLine();
+                        System.out.print("商品供应商（" + rs.getString("gongyingshang") + "）：");
+                        String supplier = sc.nextLine();
+                        pstmt = conn.prepareStatement(
+                                "UPDATE t_shangping SET mingcheng = ?, danjia = ?, gongyingshang = ? WHERE tiaoma = ?");
+                        pstmt.setString(1, name.isEmpty() ? rs.getString("mingcheng") : name);
+                        pstmt.setDouble(2, price == 0.0 ? rs.getDouble("danjia") : price);
+                        pstmt.setString(3, supplier.isEmpty() ? rs.getString("gongyingshang") : supplier);
+                        pstmt.setString(4, codeToModify);
+                        pstmt.executeUpdate();
+                        System.out.println("成功修改该商品");
+                    }
+                    break;
+                case 3:
+                    System.out.println("退出系统");
+                    break;
+                default:
+                    System.out.println("无效的选择，请重新输入");
+                    break;
+            }
+        } while (choice != 3);
+        rs.close();
+        pstmt.close();
+        conn.close();
+    }
+}