java - Variable doesn't get updated after function processes -

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i'm building calculator app 2 textviews (one formula , 1 result). result after calculations stored in variable called result left empty default. when run it, after function executes, works result variable still remains empty string. please me.

scientificcalculator.java

 int prevanswer = 0; textview formulascreen; textview resultscreen; string formuladisplay = ""; string resultdisplay = ""; string result = ""; string operator;  public void onclickequals(view view) {      toast toast = toast.maketext(getcontext(), "equals to: " + string.valueof(result), toast.length_short);     toast.show();      if (operator == "+" || operator == "-" || operator == "x" || operator == "÷") {          getresult();         updateresultdisplay();      }  }  private boolean getresult() {      if (operator == "") return false;      string[] operation = formuladisplay.split(pattern.quote(operator));      if (operation.length < 2) return false;      result = string.valueof(res.format(simpleop(operation[0], operation[1], operator)));      return true;  }  public double simpleop(string a, string b, string op) {      switch (op) {          case "+":             return double.valueof(a) + double.valueof(b);          case "-":             return double.valueof(a) - double.valueof(b);          case "x":             return double.valueof(a) * double.valueof(b);          case "÷":             return double.valueof(a) / double.valueof(b);          default:             return -1;      }  } 

you have 2 result variables: result , resultdisplay. calculation code updates result, within updateresultdisplay() use display contents of (unchanging) resultdisplay.

so need update updateresultdisplay() to

private void updateresultdisplay() {     resultscreen.settext(result); }