A quicker way is this:

public static String execCmd(String cmd) throws java.io.IOException {
    java.util.Scanner s = new java.util.Scanner(Runtime.getRuntime().exec(cmd).getInputStream()).useDelimiter("\\A");
    return s.hasNext() ? s.next() : "";
}

Which is basically a condensed version of this:

public static String execCmd(String cmd) throws java.io.IOException {
    Process proc = Runtime.getRuntime().exec(cmd);
    java.io.InputStream is = proc.getInputStream();
    java.util.Scanner s = new java.util.Scanner(is).useDelimiter("\\A");
    String val = "";
    if (s.hasNext()) {
        val = s.next();
    }
    else {
        val = "";
    }
    return val;
}

I know this question is old but I am posting this answer because I think this may be quicker.

Edit (For Java 7 and above)

Need to close Streams and Scanners. Using AutoCloseable for neat code:

public static String execCmd(String cmd) {
    String result = null;
    try (InputStream inputStream = Runtime.getRuntime().exec(cmd).getInputStream();
            Scanner s = new Scanner(inputStream).useDelimiter("\\A")) {
        result = s.hasNext() ? s.next() : null;
    } catch (IOException e) {
        e.printStackTrace();
    }
    return result;
}

well tesseract is external command so you do not need to use it with cmd. Add tesseract to environment variables. Use direct command as :

String[] commands = {"tesseract", imageFilePath, outputFilePath };

Exist status 1 means Incorrect function. See process exit status