icu4j charset detector

Detector.java

import com.ibm.icu.text.CharsetDetector;
import com.ibm.icu.text.CharsetMatch;

import java.io.BufferedInputStream;
import java.io.FileInputStream;
import java.io.IOException;

public class Detector {

    public static void main(String[] args) {

        for ( String fileName : args ) {
            try (BufferedInputStream bis = new BufferedInputStream(new FileInputStream(fileName))) {
                CharsetDetector dt = new CharsetDetector();
                dt.setText(bis);
                for( CharsetMatch csm : dt.detectAll() ) {
                    System.out.printf("%s detected encoding: %s with confidence: %d/100%n", fileName, csm.getName(), csm.getConfidence());
                }
            } catch (IOException ioe) {
                System.err.println("Error encountered detecting encoding for " + fileName);
                ioe.printStackTrace(System.err);
            }
        }
    }
}

To compile and run, you will need icu4j jar on the classpath. Assuming a suitable version is in the directory alongside the file,

$ javac -cp icu4j.jar Detector.java
$ java -cp .:icu4j.jar Detector [file, [ file2, ...]

will list out the detected encodings to standard output.