Why does my app keep crashing?

Question

I am creating an app that uses an age restriction when started and this is what I am working on first, but when I run my appit crashes immediately with no prompt and with no 'this app has stopped', notification. I am using android studio. There is no problem with android studio because I have run different sets oof code and projects and they turn out fine. It crashes on both the emulator and adb device.
I have attached the code.
Please ask for anything else and help as soon as possible

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import java.util.Scanner;

public class MainActivity extends AppCompatActivity {

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

Scanner s1 = new Scanner(System.in);
System.out.println(s1.nextInt());

int age = s1.nextInt();

if (age < 0) {
System.out.

Answer 1

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import java.util.Scanner;

public class MainActivity extends AppCompatActivity {

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

Scanner s1 = new Scanner(System.in);
System.out.println(s1.nextInt());

int age = s1.nextInt();

if (age < 0) {
System.out.println("Really");
} else if (age < 16) {
System.out.println("Sorry, you are too young for this game. Please exit!");
} else if (age < 100) {
System.out.println("Welcome!");
} else {
System.out.println("Really?");
}
}
}

Answer 2

This is the entire code👆

Answer 3

#Code