meter to inch conversion

package com.example.viraj.metertoinch;

import android.graphics.Color;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    private EditText entertext;
    private Button button;
    private TextView resultdisplay;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        entertext = (EditText) findViewById(R.id.id_enter_meter);
        resultdisplay = (TextView) findViewById(R.id.id_text_display);
        button = (Button) findViewById(R.id.id_button);
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                //1m = (1/0.0254)″ = 39.37007874″
                //conversion data
                double multiplier = 39.37007874;
                double result = 0.0;
                //is se if txt not enter it display msg
                if (entertext.getText().toString().equals("")) {
                    resultdisplay.setText("PLZ ENTER VALID NO");
                    resultdisplay.setTextColor(Color.RED);
                } else {

                    double converter = Double.parseDouble(entertext.getText().toString());
                    result = converter * multiplier;
                    //resultdisplay.setText(Double.toString(result));
                    //decimal ke bad ko formate karne ke liye %.2f   % ke bad 2 decimal tak
                    resultdisplay.setText(String.format("%.2f", result) + "inch");
                }

            }
        });
    }
}

xml code

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"

    tools:context="com.example.viraj.metertoinch.MainActivity">

    <EditText
        android:id="@+id/id_enter_meter"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="64dp"
        android:ems="10"
        android:hint="ENTER METER"
        android:inputType="textPersonName"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/textView" />

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="64dp"
        android:text="METER TO INCH CONVERTER"

        android:textColor="@android:color/holo_green_dark"
        android:textSize="24sp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <Button
        android:id="@+id/id_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="84dp"
        android:text="Button"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/id_enter_meter" />

    <TextView
        android:id="@+id/id_text_display"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_marginEnd="8dp"
        android:layout_marginStart="8dp"
        android:layout_marginTop="60dp"
        android:text="o"
        android:textSize="30dp"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/id_button" />
</android.support.constraint.ConstraintLayout>