Java命令行解析庫 Argparse4j

argparse4j 是 Python argparse 命令行解析器的 Java 語言移植版。

它的主要特性：

• Supported positional arguments and optional arguments.
• Variable number of arguments.
• Generates well formatted line-wrapped help message.
• Takes into account East Asian Width ambiguous characters when line-wrap.
• Sub-commands like, git add.
• Customizable option prefix characters, e.g. '+f' and '/h'.
• Print default values in help message.
• Choice from given collection of values.
• Type conversion from option strings.
• Can directly assign values into user defined classes using annotation.
• Group arguments so that it will be printed in help message in more readable way.

示例代碼：

import java.io.IOException;
import java.nio.ByteBuffer;
import java.nio.channels.ByteChannel;
import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.nio.file.StandardOpenOption;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import net.sourceforge.argparse4j.ArgumentParsers;
import net.sourceforge.argparse4j.inf.ArgumentParser;
import net.sourceforge.argparse4j.inf.ArgumentParserException;
import net.sourceforge.argparse4j.inf.Namespace;
public class Checksum {

public static void main(String[] args) {
    ArgumentParser parser = ArgumentParsers.newArgumentParser("Checksum")
            .defaultHelp(true)
            .description("Calculate checksum of given files.");
    parser.addArgument("-t", "--type")
            .choices("SHA-256", "SHA-512", "SHA1").setDefault("SHA-256")
            .help("Specify hash function to use");
    parser.addArgument("file").nargs("*")
            .help("File to calculate checksum");
    Namespace ns = null;
    try {
        ns = parser.parseArgs(args);
    } catch (ArgumentParserException e) {
        parser.handleError(e);
        System.exit(1);
    }
    MessageDigest digest = null;
    try {
        digest = MessageDigest.getInstance(ns.getString("type"));
    } catch (NoSuchAlgorithmException e) {
        System.err.printf("Could not get instance of algorithm %s: %s",
                ns.getString("type"), e.getMessage());
        System.exit(1);
    }
    for (String name : ns.





   





 getList("file")) {
        Path path = Paths.get(name);
        try (ByteChannel channel = Files.newByteChannel(path,
                StandardOpenOption.READ);) {
            ByteBuffer buffer = ByteBuffer.allocate(4096);
            while (channel.read(buffer) > 0) {
                buffer.flip();
                digest.update(buffer);
                buffer.clear();
            }
        } catch (IOException e) {
            System.err
                    .printf("%s: failed to read data: %s", e.getMessage());
            continue;
        }
        byte md[] = digest.digest();
        StringBuffer sb = new StringBuffer();
        for (int i = 0, len = md.length; i < len; ++i) {
            String x = Integer.toHexString(0xff & md[i]);
            if (x.length() == 1) {
                sb.append("0");
            }
            sb.append(x);
        }
        System.out.printf("%s  %s\n", sb.toString(), name);
    }
}


}
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