java illegal start of expression error

When I tried to run the code below, an error appeared:

error: illegal start of expression

What does this error mean? How will I be able to fix it?

public boolean isVowel(char c) {
    if (c == 'a' || c == 'e' || c == 'i' || c == 'o' || c == 'u' ||) {
        return true;
    }
    return false;
}