java - 在 Java 程序中加载表

Question

我有一个包含 25 行和 3-4 列的表格。我想使用这张表一次从中读取所有数据并将其存储在 Java 程序中。由于在 Java 程序的整个生命周期中我会经常需要数据，所以我不想连接到 DB 并执行查询。我怎样才能做到这一点？

Answer 1

我会创建一个类，其成员对应于表中的数据。

然后我会创建一些数据结构( map ？)，您可以通过它获取数据。

如果您需要“类似数据库”的访问权限，请使用像 Apache Derby 这样的嵌入式数据库。从外部一次性输入数据，然后将其存储在您的本地数据库中，这将具有非常灵敏的查找时间。

一些伪代码

让这个类成为你的绑定(bind)，例如......我只是做了一些东西

class MyObject {
    private final String key;
    private final long stamp;
    private final String name;
    private final int other;
    public MyObject(String key, long stamp, String name, int other) {
        this.key = key;
        this.stamp = stamp;
        this.name = name;
        this.other = other;
    }

    public String toString() {
        return name + " has an other of " + other + " and a stamp of " + stamp;
    }

}

您的应用程序可能看起来像这样

class MyApp {

    Connection con = ... // connect to DB here
    // work with DB
    ResultSet rs = ... // query the DB for your data
    Map<String, MyObject> map = new HashMap<String, MyObject>();
    while(rs.next()) {
        String key = rs.getString(1);
        long stamp = rs.getLong(2);
        String name = rs.getString(3);
        int other = rs.getInteger(4);
        MyObject obj = new MyObject(key,stamp,name,other);
        map.put(key,obj);
    }
    Map<String, MyObject> safeMap = Collections.unmodifiableMap(map);

    // spawn 5 threads (yes we should keep ref's to them - oh well
    for(int i = 0; i < 5; i++) {
        Runnable run = new SomeBackgroundProcess(i,safeMap);
        Thread t = new Thread(run);
        t.start();
    }

}

后台线程可能看起来像这样

class SomeBackgroundProcess {

    final int awesomeNumber;
    final Map<String,MyObject> map;
    SomeBackgroundProcess(int num, Map<String,MyObject> map) {
        this.awesomeNumber = num;
        this.map = map;
    }

    public void run() {
        InputStream in = // some input stream, for example
        while(true) {
            String key = in.magic(); // somehow you acquired a key!
            MyObject obj = map.get(key);
            if(obj != null) Log.log(obj.toString()); // writes out all about the object it found
        }
    }

}