Java PatternSyntaxException

My problem is: I want to enter a number and my method should remove symbols like "+","/","-","." with the help of regex (pattern & matcher). My method looks like this:

"String eingabe" is the entered number:

String bindestrich = "-";
        String plus = "+";
        String slash = "/";
        String punkt = ".";
        String leer = "";

        Pattern bindestrichP = Pattern.compile(bindestrich);
        Matcher matchBindestrich = bindestrichP.matcher(eingabe);
        eingabe = matchBindestrich.replaceAll(leer);

        Pattern plusP = Pattern.compile(plus);
        Matcher matchPlus = plusP.matcher(eingabe);
        eingabe = matchPlus.replaceAll(leer);

        Pattern slashP = Pattern.compile(slash);
        Matcher matchSlash = slashP.matcher(eingabe);
        eingabe = matchSlash.replaceAll(leer);

        Pattern punktP = Pattern.compile(punkt);
        Matcher matchPunkt = punktP.matcher(eingabe);
        eingabe = matchPunkt.replaceAll(leer);

However it throws a PatternSyntaxException already at the Pattern-making point. What do I do wrong? Is there any simpler method to remove exact these symbols?