activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.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=".MainActivity">

     <TextView android:id="@+id/textView"
         android:layout_width="wrap_content"
         android:layout_height="wrap_content"
         app:layout_constraintLeft_toLeftOf="parent"
         app:layout_constraintTop_toTopOf="parent" />

    <EditText android:id="@+id/editTextName"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:ems="10"
        android:hint="Enter your name"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        app:layout_constraintTop_toTopOf="parent"/>

    <Button android:id="@+id/button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Save"
        app:layout_constraintTop_toBottomOf="@+id/editTextName"
        app:layout_constraintLeft_toLeftOf="parent"
        app:layout_constraintRight_toRightOf="parent"
        android:onClick="saveName"/>

</androidx.constraintlayout.widget.ConstraintLayout>

MainActivity.java

package com.example.preference;

import androidx.appcompat.app.AppCompatActivity;

import android.content.SharedPreferences;
import android.os.Bundle;
import android.view.View;
import android.widget.EditText;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {

     private final String NAME="NAME";
     private EditText mEditTextName;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView textView = (TextView)findViewById(R.id.textView);
        SharedPreferences sharedPreferences = getPreferences(MODE_PRIVATE);
        String name = sharedPreferences.getString(NAME,null);
        if (name==null) {
            textView.setText("Hello");
        } else {
            textView.setText("Welcome back " + name + "!");
        }
        mEditTextName = findViewById(R.id.editTextName);
        }

        public void saveName(View view) {
            SharedPreferences.Editor editor = getPreferences(MODE_PRIVATE).edit();
            editor.putString(NAME, mEditTextName.getText().toString());
            editor.apply();
        }
}