A simple class to manage android permissions in Marshmallow version (Android 6.0) or above.

MarshmallowPermissions.java

package com.example.logintutorial;

import android.Manifest;
import android.annotation.TargetApi;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;

public class AskPermission extends AppCompatActivity {


    private static final int READ_CONTACTS_REQUEST_CODE = 1;

    @TargetApi(Build.VERSION_CODES.M)
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_ask_permission);
        /*check if we have permission or not
        returns Permission_GRANTED if we have, otherwise Permission_DENIED
         */

        // no need to check android version as these classes are of support library which already checks android version

        int permissionCheck = ContextCompat.checkSelfPermission(this, Manifest.permission.READ_CONTACTS);
        if (permissionCheck == PackageManager.PERMISSION_GRANTED) {
            // perform your work
        } else {
            // request for permission
            boolean isDeniedPreviously = ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.READ_CONTACTS);
            if (isDeniedPreviously) {
                // show an explanation as to why you need this permission and again request for permission
                // if don't ask again box is checked, and we have again asked for permission it will directly call
                // onRequestPermissionResult with Permission_DENIED result
            } else {
                // request for permission
                ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.READ_CONTACTS}, READ_CONTACTS_REQUEST_CODE); // shows the dialog

            }
        }


    }

    @Override
    public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);

        if (requestCode == READ_CONTACTS_REQUEST_CODE) {
            // if request is cancelled grantResults array is empty
            if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                // perform your work as permission is granted
            } else {
                // permission is denied so disable any functionality the app will use because of this permission
                //your app might show a dialog or snackbar explaining why it could not perform the user's requested action that needs that permission.
            }
        }
    }
}