小编Chi*_*led的帖子

我试图准确地了解Java的服务提供程序机制如何工作以找到适当的JDBC驱动程序.这是我到目前为止:

由于Class.ForName不再用于显式加载JDBC Driver,因此Java会从传递给getConnection方法的数据库url字符串中知道它需要什么类型的驱动程序.例如,连接到oracle数据库的数据库url将是这样的:

public static final String DB_URL = "jdbc:oracle:thin@//localhost:1521/ORCL";

然后,DriverManager将在projects类路径中指定的jar中查找oracle驱动程序的实现.它会在META-INF/Services每个jar的目录中查找驱动程序配置文件(其中将是实际驱动程序类的名称).在Class Loader将加载它找到的第一个比赛而忽略其他.

以上工作准确吗？如果我错过了什么或者出了什么问题,请告诉我.

如何在我的Java SWT应用程序中右键对齐复选框？这是我的代码片段:

    Button checkFullECR = new Button(scrolledForm.getBody(), SWT.CHECK);
    checkFullECR.setAlignment(SWT.RIGHT);
    checkFullECR.setBackground(SWTResourceManager.getColor(SWT.COLOR_WHITE));
    checkFullECR.setText("I need the complete ECR/ECN Process:");

它看起来如下:

[ ] I need the complete ECR/ECN Process:

我希望它看起来像:

I need the complete ECR/ECN Process:       [ ]

我有一个带按钮的片段，单击该按钮应该更改我应用程序中的主题，但是当我打开该类时，我只会收到此错误：这是 logcat

08-14 21:32:45.914  29624-29624/addid E/AndroidRuntime? FATAL EXCEPTION: main
Process: appid, PID: 29624
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.Button.setOnClickListener(android.view.View$OnClickListener)' on a null object reference
        at appid.Fragment.GuidaTv.InitView(GuidaTv.java:75)
        at appid.Fragment.GuidaTv.onCreateView(GuidaTv.java:41)
        at android.support.v4.app.Fragment.performCreateView(Fragment.java:1789)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:955)
        at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1138)
        at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:740)
        at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1501)
        at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:458)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5254)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

我的课：

public class GuidaTv extends Fragment implements View.OnClickListener{

private Button FirstThemButton;
private Button SecondThemButton;
private Button ThirdThemButton;
private SharedPreferences sharePrefences;
private …

我使用a ExecutorService有多个线程将文本写入文件,但我无法设法同步run()方法,而不是正确的逐行字符串我问,我有一个字符串的所有字符的混合,因为他们写它同时.

import java.io.BufferedReader
...

class WriteDns implements Runnable {

File file;
String text;

WriteDns(File file, String text) {
    this.file = file;
    this.text = text;
}

public void run() {
    synchronized (this) {
        try (BufferedWriter bw = new BufferedWriter(new OutputStreamWriter(
                new FileOutputStream(file)))) {
            bw.write(turnDns() + "\n");
        } catch (IOException e) {
            System.out.println("Error");
        }
    }
}

public String turnDns() {
    int space = text.indexOf(' ');
    String ip = text.substring(0, space);
    String theRest = text.substring(space);
    String temp = ip; …