Simple way to create a CRC code to a File within any JAR file, using Spring Boot and Lambda!

DemoFileCRCApplication

package com.example;

import java.io.File;
import java.io.InputStream;
import java.util.Enumeration;
import java.util.jar.JarEntry;
import java.util.jar.JarFile;
import java.util.zip.CRC32;

import lombok.extern.slf4j.Slf4j;

import org.springframework.boot.ExitCodeGenerator;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.context.ConfigurableApplicationContext;

@SpringBootApplication
@Slf4j
public class DemoFileCRCApplication {

	public static void main(String[] args) throws Exception {
		final ConfigurableApplicationContext runContext = SpringApplication.run(DemoFileCRCApplication.class, args);

		final String jarFilePath = "[JAR PATH GOES HERE]";

		JarFile jar = new JarFile(new File(jarFilePath));

		Enumeration<JarEntry> entries = jar.entries();

		while (entries.hasMoreElements()) {
			JarEntry jarEntry = entries.nextElement();
			
			updateFileCRC(jarEntry, jar);
			
			log.info("File Name " + jarEntry.getName() + " - CRC = " + jarEntry.getCrc());
		}

		jar.close();

		SpringApplication.exit(runContext, OK);
		
	}
	
	private static void updateFileCRC(final JarEntry jarEntry, final JarFile jar) throws Exception {
		if (!jarEntry.isDirectory() && jarEntry.getCrc() == 0L) {
			
			// Generates a new CRC for File
			CRC32 newCRC = new CRC32();
			InputStream jarEntryIS = jar.getInputStream(jarEntry);
			int i;
			
			while ( (i = jarEntryIS.read()) != -1) newCRC.update(i);
			
			jarEntry.setCrc(newCRC.getValue());
			
			log.info(">>>>>>>>>>>> Created CRC for file " + jarEntry.getName() + "=" + jarEntry.getCrc());
		}
	}
	
	private static final ExitCodeGenerator OK = () -> 100; // LAMBDA!
}