Java:检查命令行参数是否为空 [英] Java: Check if command line arguments are null

问题描述

我希望对我的命令行参数进行一些错误检查

I am looking to do some error checking for my command line arguments

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

然而，这会返回一个数组越界异常，这是有道理的.我只是在寻找正确的用法.

However, this returns an array out of bounds exception, which makes sense. I am just looking for the proper usage.

推荐答案

参数永远不能为 null.他们只是不会存在.

The arguments can never be null. They just wont exist.

换句话说，您需要做的是检查参数的长度.

In other words, what you need to do is check the length of your arguments.

public static void main(String[] args)
{
    // Check how many arguments were passed in
    if(args.length == 0)
    {
        System.out.println("Proper Usage is: java program filename");
        System.exit(0);
    }
}

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