Java main 参数 args

Java: Check if command line arguments are null, http://stackoverflow.com/questions/3868878/java-check-if-command-line-arguments-are-null

Command-Line Arguments, Command-Line Argumentshttp://docs.oracle.com/javase/tutorial/essential/environment/cmdLineArgs.html

检查 args 是否为 null

You should check for (args == null || args.length == 0). Although the null check isn't really needed, it is a good practice.

一段有趣的代码：

public class Test
{
	public static void main(String[] args) throws InterruptedException
	{
		String [] dummy= new String [] {};
		if(dummy == null)
		{
			System.out.println("Proper Usage is: java program filename");
			System.exit(0);
		}
	}
}

上面这个例子跟String[] args 道理一样

String[] dummy = new String[] {"123","abc"};

public class Test
{
	public static void main(String[] args) throws InterruptedException
	{
		String [] dummy= new String [] {};
		if(dummy.length == 0)
		{
			System.out.println("haha.");
		}
	}
}