How to check multiple strings are null java?

There's so much wrong here.

First, if null values from the database are invalid, those values never should have been allowed to be null when written to the database.

Next, you keep saying "string" and the value should be "0.0". Well, that's a floating-point number, nut really a string. So what is the value type supposed to be? A string or a float? The value you set should NOT be "0.0", but instead should be 0.0. Why would you set the value to "0.0" when you cannot do math with a string? See the difference?

Again, if this is supposed to be a floating-point number in this field, storing it in the database as a string is a really bad idea and should be fixed there.

Next, you can simply do what you are describing, no matter how bad your data handling is, with a simple function that takes a string as a parameter and returns a string:

function string ValidateString(string value) {
    string returnValue = value;

    if (string.IsNullOrEmpty(value)
    {
        returnValue = "0.0";
    }

    return returnValue;
}

Then you simply call it for each field you want to validate:

someField = ValidateString(someDatabaseField);

Cursor res_p;
		res_p = db.sumProfits();
		res_p.moveToNext();
		total_profits = res_p.getString(0);

sum()

total() total()

value = readerObj.getDouble(columnNumber);