Determine whether a file is a JAR File. : Jar File « File Input Output « Java

1. Java
2. File Input Output
3. Jar File

Determine whether a file is a JAR File.

  
import java.io.BufferedInputStream;
import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.util.zip.ZipFile;

public class Main {

  /**
   * Determine whether a file is a JAR File.
   */
  public static boolean isJarFile(File file) throws IOException {
    if (!isZipFile(file)) {
      return false;
    }
    ZipFile zip = new ZipFile(file);
    boolean manifest = zip.getEntry("META-INF/MANIFEST.MF") != null;
    zip.close();
    return manifest;
  }
  /**
   * Determine whether a file is a ZIP File.
   */
  public static boolean isZipFile(File file) throws IOException {
      if(file.isDirectory()) {
          return false;
      }
      if(!file.canRead()) {
          throw new IOException("Cannot read file "+file.getAbsolutePath());
      }
      if(file.length() < 4) {
          return false;
      }
      DataInputStream in = new DataInputStream(new BufferedInputStream(new FileInputStream(file)));
      int test = in.readInt();
      in.close();
      return test == 0x504b0304;
  }
}

   
    
  

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