JOPT SIMPLE framework Implementing command line help and use instructions

The Jopt Simple framework is a Java library for handling command line parameters.It can help us quickly realize the command line help and use instructions.This article will introduce in detail how to use the Jopt Simple framework to generate command lines to help and use instructions, and provide the corresponding Java code example. The JOPT SIMPLE framework mainly analyzes the line parameters by creating the OptionParser object.We can add various command line options and parameters through the OptionParser object, set the description and default value of the option, and even add the verification rules of the command line parameter. First, we need to introduce the job simple library in the Java project.You can add it to the dependencies of the project through building tools such as Maven or Gradle. Then, we can create a class to process the command line parameters.The following is a simple example: import joptsimple.OptionParser; import joptsimple.OptionSet; public class CommandLineApp { public static void main(String[] args) { OptionParser parser = new OptionParser(); // Add command line options parser.accepts("help").forHelp(); Parser.Accepts ("input"). Withrequiredarg (). Descripedas ("Enter file") .Required (); Parser.Accepts ("Output"). Withrequiredarg (). Describedas ("Output file") .DefaultSto ("Output.txt"); OptionSet options = parser.parse(args); // Process command line options if (options.has("help")) { parser.printHelpOn(System.out); return; } String inputFile = (String) options.valueOf("input"); String outputFile = (String) options.valueOf("output"); // Other processing logic System.out.println ("Input file:" + InputFile); System.out.println ("Output file:" + outputFile); } } In the above example, we created an OptionParser object and added three command line options through the Accepts method: Help, input, and output.Among them, the HELP option is for the help option to print the command line help information.The INPUT option is used to specify the input file, the Output option is used to specify the output file, and the default is output.txt. After parsing the command line parameters, we can determine whether the help option is passed through the Optionset object.If you pass the help option, print the command line to help information through the Printhelpon method.Otherwise, we can obtain the value of the input file and the output file through the valueof method, and perform subsequent processing logic. Next, we can compile and run the above code.Execute the following commands in the command line: shell java CommandLineApp --help Will print similar help information: Option Description ------ ----------- Help shows this help information Input = <Entry file> Enter file, default is necessary output = <Output file> Output file, the default is output.txt If we execute the following command: shell java CommandLineApp --input input.txt --output output.txt The following results will be printed: Enter file: input.txt Output file: output.txt Through the above examples, we can find that the Jopt Simple framework is very convenient to achieve the generation of command line help and use instructions.We can add more command line options and parameters according to actual needs. It should be noted that this is just a simple example of Jopt Simple.Jopt Simple also provides other rich functions and options, which can be processed more complicated according to demand.