I am trying to accept a string with any of the following variations into my method:

"11+6i"
"11-6i"
"-11-6i"

Using the code I have below, the first two work correctly but for some reason when the string contains two "-" characters I cannot seem to parse it correctly. 

Is there anyway to modify my code for it to be able to parse "-11-6i" as well?

Here is my code thus far:

```
if (passedString.contains("+")) {

        int i = passedString.indexOf("+");
        int endIndex = passedString.indexOf("i");

        String real = passedString.substring(0, i);

        String imag = passedString.substring(i, endIndex);

        MyDouble realNum = new MyDouble(Double.parseDouble(real));
        MyDouble imagNum = new MyDouble(Double.parseDouble(imag));

        cn = new ComplexNumber(realNum, imagNum);

    } else {

        int i = passedString.indexOf("-");

        int endIndex = passedString.indexOf("i");

        String real = passedString.substring(0, i);

        String imag = passedString.substring(i, endIndex);

        MyDouble realNum = new MyDouble(Double.parseDouble(real));
        MyDouble imagNum = new MyDouble(Double.parseDouble(imag));

        cn = new ComplexNumber(realNum, imagNum);

    }

```