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Java 创建一个类以从derby数据库获取值_Java_Arrays_Derby - Fatal编程技术网

Java 创建一个类以从derby数据库获取值

Java 创建一个类以从derby数据库获取值,java,arrays,derby,Java,Arrays,Derby,我创建了一个类来连接derby数据库。在程序中,我创建了表并插入了一些水果名称作为值。我只是想知道如何创建另一个类以在新数组中获取水果名称值 import java.sql.Connection; import java.sql.DriverManager; import java.sql.ResultSet; import java.sql.ResultSetMetaData; import java.sql.Statement; public class FruitDatabase {

我创建了一个类来连接derby数据库。在程序中,我创建了表并插入了一些水果名称作为值。我只是想知道如何创建另一个类以在新数组中获取水果名称值

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;

public class FruitDatabase {

    public static void main(String[] args) throws Exception {
        Connection conn = getConnection();
        Statement stmt = conn.createStatement();

        stmt.executeUpdate("drop table fruit");
        stmt.executeUpdate("create table fruit (name CHAR(15))"); 
        stmt.executeUpdate("INSERT INTO fruit(name)VALUES('Apple')"); 
        stmt.executeUpdate("INSERT INTO fruit(name)VALUES('Orange')");
        stmt.executeUpdate("INSERT INTO fruit(name)VALUES('Banana')");
        stmt.executeUpdate("INSERT INTO fruit(name)VALUES('Pineapple')");
        stmt.executeUpdate("INSERT INTO fruit(name)VALUES('Mango')");
        stmt.executeUpdate("INSERT INTO fruit(name)VALUES('Kiwi')");
        stmt.executeUpdate("INSERT INTO fruit(name)VALUES('Grape')");
        stmt.executeUpdate("INSERT INTO fruit(name)VALUES('Strawberry')");
        stmt.executeUpdate("INSERT INTO fruit(name)VALUES('Pear')");
        stmt.executeUpdate("INSERT INTO fruit(name)VALUES('Peach')");
        ResultSet rs = stmt.executeQuery("SELECT * FROM fruit"); 
        outputResultSet(rs);

        rs.close();
        stmt.close();
        conn.close();
    }

    private static void outputResultSet(ResultSet rs) throws Exception {
        ResultSetMetaData rsMetaData = rs.getMetaData();
        int numberOfColumns = rsMetaData.getColumnCount();
        for (int i = 1; i < numberOfColumns + 1; i++) {
            String columnName = rsMetaData.getColumnName(i);
            System.out.print(columnName + "   ");

        }
        System.out.println();
        System.out.println("----------------------");

        String array [] = new String [numberOfColumns + 1];

        while (rs.next()) {
            for (int i = 1; i < numberOfColumns + 1; i++) {
                array[i] = rs.getString(i);
                System.out.println(array[i]);
            }

        }

    }

    private static Connection getConnection() throws Exception {
        Class.forName("org.apache.derby.jdbc.EmbeddedDriver");
        String url = "jdbc:derby:MyDbTest;create=true";
        return DriverManager.getConnection(url);
    }

}
将声明为私有变量的数组,在静态块中初始化它,并为其添加getter和setter方法。这里没有使用getter setter,但这只是为了您的理解

FruitDatabase.java


我没有完全理解这个问题?是否要使用select查询从数据库中获取水果名称?这就是你要问的吗?实际上,这是我的导师编写的soem代码。我被要求在屏幕上随机显示水果名称。我已经运行了这个程序,所有的值都存储在一列中。我想创建另一个类,从上述程序的数组中获取值。非常感谢mtk,让我试试。我希望我能做到!嗨,mtk,谢谢你的帮助。事实上,我对java非常陌生。我只是不知道我应该把第一部分的代码放在哪里。这个作业对我来说很难。我看到了这个错误,因为outputResultSet是一个静态方法,我们不能按原样使用上面的代码。将更新.C:\Users\bauyeung\Documents\JCreator LE\MyProjects\Hangman\src\FruitDatabase.java:32:错误:非静态变量无法从静态上下文引用此变量。此数组=数组;^Display.java的1个错误和以下错误
public class FruitDatabase {
    private static String[] array;

    public static String[] getArray() {
        return array;
    }

    public static void setArray(String[] arr) {
        array = arr;
    }

    public static void main(String[] args) throws Exception {
    ...
    }

    private static void outputResultSet(ResultSet rs) throws Exception {
    ... 
    while (rs.next()) {
            for (int i = 1; i < numberOfColumns + 1; i++) {
                array[i] = rs.getString(i);
                System.out.println(array[i]);
            }
    setArray(array);
    ....
    }
    ....
}
public class Display {
    public static void main(String[] args) {
        String[] newArr = new String[FruitDatabase.getArray().length];
    int i=0;
    for(String s : FruitDatabase.getArray()){
        System.out.println(s);
            newArr[i++]=s;
    }
    }
}