Java Calculator error: Exception in thread "AWI-EventQueue-0" java.lang.IndexOutOfBoundsException: x = 2, Size: 2

Question

Hi I am attempting to create a calculator where the user inputs as many numbers it likes with as many operators. So for example, inputs could be "45+56*78". It is stored as a string. I have created two methods, one method which simply groups the digits together to identify whole numbers and then store them in an arraylist in the correct order with the operators. The other method simply carries out the calculation on the numbers and operators. However, whilst I get no compilation errors, I do get an error when I input a calculation and press on the equal sign button.

The error when I input "3+4" is : Exception in thread "AWI-EventQueue-0" java.lang.IndexOutOfBoundsException: x = 2, Size: 2

I have been looking at my two methods for a while now and still cannot find the error, Can anyone help please? Thank you.

 ActionListener button_eqListener = new ActionListener(){
        @Override
        public void actionPerformed(ActionEvent e){
            label2.setText(calculation(splitLabel(label.getText()))); //clicking the equal button calls the methods.
        }
    };  


public ArrayList<String> splitLabel(String val){
    ArrayList<String> label_split = new ArrayList<String>();
    String value = "";
    String op = "";

    for (int i = 0; i< val.length(); i++){
        boolean isDigit = Character.toString(val.charAt(i)).matches("[0123456789.]+");
        boolean isOperator = Character.toString(val.charAt(i)).matches("[+*/-]+");

        if (isDigit && !op.equals("")){
            String num = Character.toString(val.charAt(i));
            value = value + num;
            label_split.add(op);
            op = "";
        }else if (isDigit && op.equals("")){
            String num = Character.toString(val.charAt(i));
            value = value + num;
        } else if (isOperator && !value.equals("")){
            label_split.add(value);
            value = "";
            op = Character.toString(val.charAt(i));
        } else if (isOperator && value.equals("")){
            if (Character.toString(val.charAt(i)).equals("-")){
                value = Character.toString(val.charAt(i));
            }
        } else if (i== val.length()-1 && !value.equals("")){
            label_split.add(value);
        }
    } return label_split;
}

public String calculation(ArrayList<String> label_split){
    Double value = 0.0;
    for (int i=0; i <= label_split.size()-1; i++){
        boolean isDigit = label_split.get(i).matches("[0123456789.-]+");
        boolean isOperator = label_split.get(i).matches("[+*/-]+");         
        if (isDigit && value == 0){
            value = Double.parseDouble(label_split.get(i));
        } else if (isOperator) {
            if (label_split.get(i).equals("+")){
                boolean isDigit1 = label_split.get(i+1).matches("[0123456789.-]+");
                if (isDigit1){
                    value = value + Double.parseDouble(label_split.get(i+1));
                }
            } else if (label_split.get(i).equals("-")){
                boolean isDigit1 = label_split.get(i+1).matches("[0123456789.-]+");
                if (isDigit1){
                    value = value - Double.parseDouble(label_split.get(i+1));
                }
            } else if (label_split.get(i).equals("*")){
                boolean isDigit1 = label_split.get(i+1).matches("[0123456789.-]+");
                if (isDigit1){
                    value = value * Double.parseDouble(label_split.get(i+1));
                }
            } else if (label_split.get(i).equals("/")){
                boolean isDigit1 = label_split.get(i+1).matches("[0123456789.-]+");
                if (isDigit1){
                    value = value / Double.parseDouble(label_split.get(i+1));
                }
            } 
        }
    }
    if ((Double.toString(value)).length()>= 11){
        String error = "ERROR";
        return error;
    } else {
        return Double.toString(value);
    }
}