import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.Toast;
import java.util.regex.Pattern;
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
 Button btnone, btntwo,btnthree,btnfour,btnfive,btnsix,btnseven,btneight,btnnine,btnzero;
 Button btnAdd, btnSub, btnMul, btnDiv;
 Button btnClear, btnEqual, btnDot;
 EditText txtResult;
  @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.activity_main);
  btnone=(Button) findViewById(R.id.btn_1);
  btnone.setOnClickListener(this);
  btntwo=(Button) findViewById(R.id.btn_2);
  btntwo.setOnClickListener(this);
  btnthree=(Button) findViewById(R.id.btn_3);
  btnthree.setOnClickListener(this);
  btnfour=(Button) findViewById(R.id.btn_4);
  btnfour.setOnClickListener(this);
  btnfive=(Button) findViewById(R.id.btn_5);
  btnfive.setOnClickListener(this);
  btnsix=(Button) findViewById(R.id.btn_6);
  btnsix.setOnClickListener(this);
  btnseven=(Button) findViewById(R.id.btn_7);
  btnseven.setOnClickListener(this);
  btneight=(Button) findViewById(R.id.btn_8);
  btneight.setOnClickListener(this);
  btnnine=(Button) findViewById(R.id.btn_9);
  btnnine.setOnClickListener(this);
  btnzero=(Button) findViewById(R.id.btn_0);
  btnzero.setOnClickListener(this);
  btnAdd=(Button) findViewById(R.id.btn_plus);
  btnAdd.setOnClickListener(this);
  btnSub=(Button) findViewById(R.id.btn_minus);
  btnSub.setOnClickListener(this);
  btnMul=(Button) findViewById(R.id.btn_mul);
  btnMul.setOnClickListener(this);
  btnDiv=(Button) findViewById(R.id.btn_div);
  btnDiv.setOnClickListener(this);
  btnDot=(Button) findViewById(R.id.btn_dot);
  btnDot.setOnClickListener(this);
  btnClear=(Button) findViewById(R.id.btn_clear);
  btnClear.setOnClickListener(this);
  btnEqual=(Button) findViewById(R.id.btn_equals);
  btnEqual.setOnClickListener(this);
  txtResult=(EditText) findViewById(R.id.Edit_Txt);
  txtResult.setText("");
 }
 @Override
 public void onClick(View v) {
   if(v.equals(btnone))
    txtResult.append("1");
   if(v.equals(btntwo))
    txtResult.append("2");
   if(v.equals(btnthree))
    txtResult.append("3");
  if(v.equals(btnfour))
   txtResult.append("4");
  if(v.equals(btnfive))
   txtResult.append("5");
  if(v.equals(btnsix))
   txtResult.append("6");
  if(v.equals(btnseven))
   txtResult.append("7");
  if(v.equals(btneight))
   txtResult.append("8");
  if(v.equals(btnnine))
   txtResult.append("9");
  if(v.equals(btnzero))
   txtResult.append("0");
  if(v.equals(btnDot))
   txtResult.append(".");
  if(v.equals(btnAdd))
   txtResult.append("+");
  if(v.equals(btnSub))
   txtResult.append("-");
  if(v.equals(btnMul))
   txtResult.append("*");
  if(v.equals(btnDiv))
   txtResult.append("/");
  if(v.equals(btnClear))
   txtResult.setText("");
  if(v.equals(btnEqual))
  {
   try {
     String data = txtResult.getText().toString();
     if(data.contains("/")){
      divide(data);
     } else if(data.contains("*")){
      multiplication(data);
     } else if(data.contains("+")){
      addition(data);
     } else if(data.contains("-")){
      subtraction(data);
     }
   } catch(Exception e){
    displayInvalidMessage("Invalid Input");
   }
  }
 }
 private void displayInvalidMessage(String mes) {
  Toast.makeText(getBaseContext(),mes,Toast.LENGTH_LONG).show();
 }
 private void subtraction(String data) {
   String[] operands=data.split("-");
   if(operands.length==2){
    double operand1=Double.parseDouble(operands[0]);
    double operand2=Double.parseDouble(operands[1]);
    double result=operand1-operand2;
    txtResult.setText(String.valueOf(result));
   } else{
    displayInvalidMessage("Invalid Input");
   }
 }
 private void addition(String data) {
  String[] operands=data.split(Pattern.quote("+"));
  if(operands.length==2){
   double operand1=Double.parseDouble(operands[0]);
   double operand2=Double.parseDouble(operands[1]);
   double result=operand1+operand2;
   txtResult.setText(String.valueOf(result));
  } else{
   displayInvalidMessage("Invalid Input");
  }
 }
 private void multiplication(String data) {
  String[] operands=data.split(Pattern.quote("*"));
  if(operands.length==2){
   double operand1=Double.parseDouble(operands[0]);
   double operand2=Double.parseDouble(operands[1]);
   double result=operand1*operand2;
   txtResult.setText(String.valueOf(result));
  } else{
   displayInvalidMessage("Invalid Input");
  }
 }
 private void divide(String data) {
  String[] operands=data.split("/");
  if(operands.length==2){
   double operand1=Double.parseDouble(operands[0]);
   double operand2=Double.parseDouble(operands[1]);
   double result=operand1/operand2;
   txtResult.setText(String.valueOf(result));
  } else{
   displayInvalidMessage("Invalid Input");
  }
 }
}