到达main方法的末尾时程序不会终止

问题描述：

我有一个程序，在启动该程序之前，需要用户的输入.

I have a program where I ask for an input from the user before I launch it.

public static void main(String args[]) 
{
    String database = JOptionPane.showInputDialog(new JFrame(), "Enter a DB:");
    if(database!=null && database.foundInDB()) {
        SPVerification spv = new SPVerification();
        spv.setVisible(true);
    }
    //System.exit(1);  Without it the program doesn't terminate although it's the end
    //                 of the main function.                  
}

如果用户输入未找到的数据库，则不应执行该程序.

If the user enters a database that's not found, the program shouldn't be executed.

当我输入错误的数据库名称时，if语句下面的代码不会执行，因此我到达了main方法的末尾，但是程序没有终止，但是如果我在if之后添加了system.exit(1) if语句，程序终止.尽管我已经到达main的末尾，为什么我仍然需要打电话给System.exit(1)?

When I enter a wrong DB name, the code below if statement doesn't execute, so I reach the end of the main method, but the program doesn't terminate, but if I add system.exit(1) after the if statement, the program terminates. Why do I need to call System.exit(1) although I've reached the end of main?

答

您已经创建了一个新的JFrame，默认情况下它不会关闭，因为没有任何东西可以触发要处置的窗户，例如WindowEvent .由于这似乎是基于非UI的应用程序，因此您可以简单地使用:

You have created a new JFrame which, by default, will not close as there is nothing to trigger the window to be disposed such as a WindowEvent. As this appears to be a non-UI based application, you could simply use:

JOptionPane.showInputDialog(null, "Enter a DB:");

到达main方法的末尾时程序不会终止

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