Request and Check RunTime Permissions

Manifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.tutorialscafe.readallsms">

    <uses-permission android:name="android.permission.READ_CONTACTS" />

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity"
            android:windowSoftInputMode="stateHidden">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>

RequestRunTimePermissions.java

 @Override
    public void onRequestPermissionsResult(int requestCode, String permissions[],int[] grantResults) {
        switch (requestCode) {
            case 999: {
                // If request is cancelled, the result arrays are empty.
                if (grantResults.length > 0
                        && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
                    Toast.makeText(this, "Permission Granted.", Toast.LENGTH_SHORT).show();
                    // permission was granted, yay! Do the
                    // contacts-related task you need to do.

                } else {
                    Toast.makeText(this, "Permission Denied.", Toast.LENGTH_SHORT).show();
                    // permission denied, boo! Disable the
                    // functionality that depends on this permission.
                }
                return;
            }

            // other 'case' lines to check for other
            // permissions this app might request
        }
    }

    public void requestPermission(){
        if (ContextCompat.checkSelfPermission(MainActivity.this, Manifest.permission.READ_CONTACTS) != PackageManager.PERMISSION_GRANTED)
        {
            if(!ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this,Manifest.permission.READ_CONTACTS)){
            }else{
                ActivityCompat.requestPermissions(MainActivity.this,new String[]{Manifest.permission.READ_CONTACTS},999);
            }
        }else{
            Toast.makeText(this, "Already has permissions.", Toast.LENGTH_SHORT).show();
        }
    }