add MainActivity.java

Count/MainActivity.java

+package com.example.count;
+
+import androidx.annotation.NonNull;
+import androidx.appcompat.app.AppCompatActivity;
+
+import android.content.Intent;
+import android.os.Bundle;
+import android.util.Log;
+import android.view.View;
+import android.widget.Button;
+import android.widget.EditText;
+import android.widget.ProgressBar;
+import android.widget.Toast;
+
+public class MainActivity extends AppCompatActivity {
+
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_main);
+        Button btn = findViewById(R.id.lin);
+
+        btn.setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                startActivity(new Intent(MainActivity.this, StudentID.class));
+
+            }
+        });
+    }
+}