Cube and square:

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">

<EditText
    android:id="@+id/num"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="97dp"
    android:layout_marginTop="125dp"
    android:layout_marginEnd="104dp"
    android:layout_marginBottom="54dp"
    android:ems="10"
    android:hint="@string/app_name"
    android:inputType="number"
    android:minHeight="48dp"
    app:layout_constraintBottom_toTopOf="@+id/square"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent" />

<Button
    android:id="@+id/square"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="64dp"
    android:layout_marginTop="54dp"
    android:layout_marginEnd="62dp"
    android:layout_marginBottom="459dp"
    android:text="square"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toStartOf="@+id/cube"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/num" />

<Button
    android:id="@+id/cube"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginStart="64dp"
    android:layout_marginTop="150dp"
    android:layout_marginEnd="62dp"
    android:layout_marginBottom="459dp"
    android:text="cube"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toEndOf="@+id/square"
    app:layout_constraintTop_toBottomOf="@+id/num"
    app:layout_constraintVertical_bias="0.823" />

<TextView
    android:id="@+id/textView"
    android:layout_width="113dp"
    android:layout_height="39dp"
    android:layout_marginStart="182dp"
    android:layout_marginTop="221dp"
    android:layout_marginEnd="171dp"
    android:layout_marginBottom="347dp"
    android:text="ans"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/num" />

</androidx.constraintlayout.widget.ConstraintLayout>

Mainactivity.java
package com.example.square_and_cube;

import androidx.appcompat.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 n1;
private Button b1,b2;
private TextView t1;
Double a,sq,cu;

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

    n1=(EditText) findViewById(R.id.num);
    b1=(Button) findViewById(R.id.square);
    b2=(Button) findViewById(R.id.cube);
    t1=(TextView) findViewById(R.id.textView);

    b1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            a=Double.parseDouble(n1.getText().toString());
            sq=a*a;
            t1.setText("square : "+sq);

        }
    });
    b2.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            a=Double.parseDouble(n1.getText().toString());
            cu=a*a*a;
            t1.setText("cube : "+cu);

        }
    });
}

}