How to evauluate a numeric expression in android java ?

package com.deepesh.calculatorx;
import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class Cal_page extends AppCompatActivity {

    TextView displayer;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_cal_page);


        displayer=findViewById(R.id.displayer);
       
    }

    public void Addone(View view) {

        displayer.append("1");
    }

    public void Addtwo(View view) {
        displayer.append("2");
    }

    public void Addthree(View view) {
        displayer.append("3");
    }

    public void Addfour(View view) {
        displayer.append("4");
    }

    public void Addfive(View view) {
        displayer.append("5");
    }

    public void Addsix(View view) {
        displayer.append("6");
    }

    public void Addseven(View view) {
        displayer.append("7");
    }

    public void Addeight(View view) {
        displayer.append("8");
    }

    public void Addnine(View view) {
        displayer.append("9");
    }

    public void Addzero(View view) {
        displayer.append("0");
    }


    public void Addplus(View view) {
        displayer.append("+");
    }

    public void Addsubtract(View view) {
        displayer.append("-");
    }

    public void Addmultiply(View view) {
        displayer.append("*");
    }

    public void AddDivide(View view) {
        displayer.append("/");
    }

    public void AddDot(View view) {
        displayer.append(".");
    }

    public void clearALL(View view){
        displayer.setText(" ");
    }

    public void GetResult(View view) {
   //user presses Equal sign
        //evauluate the numeric expression and get result

    }

    public void clearLastchar(View view) {

        CharSequence numbers = displayer.getText();
        String Snumbers = numbers.toString();

        String Nnumbers = Snumbers.substring(0,Snumbers.length()-1);

        displayer.setText(Nnumbers);

    }
}