Im new to android how can i set random activities to my results button

Im having 4 activities other than mainactivity. I have added results button and when the user click on that button a random activity should be opened. Heres my main activity class and its xml

package tk.crazyapps.www.volleyupload;

    import android.app.ProgressDialog;
    import android.content.Intent;
    import android.graphics.Bitmap;
    import android.net.Uri;
    import android.provider.MediaStore;
    import android.support.v7.app.AppCompatActivity;
    import android.os.Bundle;
    import android.util.Base64;
    import android.view.Menu;
    import android.view.MenuItem;
    import android.view.View;
    import android.widget.Button;
    import android.widget.EditText;
    import android.widget.ImageView;
    import android.widget.Toast;

    import com.android.volley.AuthFailureError;
    import com.android.volley.Request;
    import com.android.volley.RequestQueue;
    import com.android.volley.Response;
    import com.android.volley.VolleyError;
    import com.android.volley.toolbox.StringRequest;
    import com.android.volley.toolbox.Volley;

    import java.io.ByteArrayOutputStream;
    import java.io.IOException;
    import java.util.ArrayList;
    import java.util.Hashtable;
    import java.util.Map;
    import java.util.Random;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

private Button buttonChoose;
private Button buttonUpload;

private ImageView imageView;

private EditText editTextName;

private Bitmap bitmap;

private int PICK_IMAGE_REQUEST = 1;

private String UPLOAD_URL ="http://ift.tt/2aIQlcL";

private String KEY_IMAGE = "image";
private String KEY_NAME = "name";

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

    buttonChoose = (Button) findViewById(R.id.buttonChoose);
    buttonUpload = (Button) findViewById(R.id.buttonUpload);

    editTextName = (EditText) findViewById(R.id.editText);

    imageView  = (ImageView) findViewById(R.id.imageView);

    buttonChoose.setOnClickListener(this);
    buttonUpload.setOnClickListener(this);









}



public String getStringImage(Bitmap bmp){
    ByteArrayOutputStream baos = new ByteArrayOutputStream();
    bmp.compress(Bitmap.CompressFormat.JPEG, 100, baos);
    byte[] imageBytes = baos.toByteArray();
    String encodedImage = Base64.encodeToString(imageBytes, Base64.DEFAULT);
    return encodedImage;
}

private void uploadImage(){
    //Showing the progress dialog
    final ProgressDialog loading = ProgressDialog.show(this,"Uploading...","Please wait...",false,false);
    StringRequest stringRequest = new StringRequest(Request.Method.POST, UPLOAD_URL,
            new Response.Listener<String>() {
                @Override
                public void onResponse(String s) {
                    //Disimissing the progress dialog
                    loading.dismiss();
                    //Showing toast message of the response
                    Toast.makeText(MainActivity.this, s , Toast.LENGTH_LONG).show();
                }
            },
            new Response.ErrorListener() {
                @Override
                public void onErrorResponse(VolleyError volleyError) {
                    //Dismissing the progress dialog
                    loading.dismiss();

                    //Showing toast
                    Toast.makeText(MainActivity.this, volleyError.getMessage().toString(), Toast.LENGTH_LONG).show();
                }
            }){
        @Override
        protected Map<String, String> getParams() throws AuthFailureError {
            //Converting Bitmap to String
            String image = getStringImage(bitmap);

            //Getting Image Name
            String name = editTextName.getText().toString().trim();

            //Creating parameters
            Map<String,String> params = new Hashtable<String, String>();

            //Adding parameters
            params.put(KEY_IMAGE, image);
            params.put(KEY_NAME, name);

            //returning parameters
            return params;
        }
    };

    //Creating a Request Queue
    RequestQueue requestQueue = Volley.newRequestQueue(this);

    //Adding request to the queue
    requestQueue.add(stringRequest);
}

private void showFileChooser() {
    Intent intent = new Intent();
    intent.setType("image/*");
    intent.setAction(Intent.ACTION_GET_CONTENT);
    startActivityForResult(Intent.createChooser(intent, "Select Picture"), PICK_IMAGE_REQUEST);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    super.onActivityResult(requestCode, resultCode, data);

    if (requestCode == PICK_IMAGE_REQUEST && resultCode == RESULT_OK && data != null && data.getData() != null) {
        Uri filePath = data.getData();
        try {
            //Getting the Bitmap from Gallery
            bitmap = MediaStore.Images.Media.getBitmap(getContentResolver(), filePath);
            //Setting the Bitmap to ImageView
            imageView.setImageBitmap(bitmap);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

@Override
public void onClick(View v) {

    if(v == buttonChoose){
        showFileChooser();
    }

    if(v == buttonUpload){
        uploadImage();
    }
}

****Heres the xml of main activity****

<Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Choose Image"
    android:id="@+id/buttonChoose" />


<ImageView
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_weight="1"
    android:id="@+id/imageView" />


<EditText
    android:id="@+id/editText"
    android:hint="Enter ur Name"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    />


<Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Upload Image"
    android:id="@+id/buttonUpload" />
<Button
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:text="Results"
    android:id="@+id/buttonresult" />