This is a class that can be used to Validate phone numbers in Tanzania based on a telecomm network, or if it fits the standard phone number format. It can also accept unformated number and return one that fits the format.

TZPhoneNumberUtils.java

/*
 * Copyright (c) 2018, Yusuph Wickama (WickerLabs). All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are met:
 *
 *  Redistributions of source code must retain the above copyright notice, this
 *   list of conditions and the following disclaimer.
 *
 *  Redistributions in binary form must reproduce the above copyright notice,
 *   this list of conditions and the following disclaimer in the documentation
 *   and/or other materials provided with the distribution.
 *
 * THIS CLASS IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
 * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
 * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
 * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

package com.wickerlabs.gasdelivery.util;

public class TZPhoneNumberUtils {

    /*
     * This can be adapted to any number format of any telecoms networks in Tanzania.
     * The example below detects whether the number is a valid TTCL issued number following the standard number format.
     * It will return `true` for numbers such as the ones below and may other that fit the standard:
     * '+255639123456','+255739123456','255739123456','0639123456','0739123456'
     * */

    public static boolean isTTCL(String phoneNumber) {
        /*
        * Here the (63|73) capture group defines the format for TTCL.
        * So for TiGO it may look something like (65|67|71)
        * */

        phoneNumber = phoneNumber.replaceAll("\\s+",""); // Clear spaces

        String regex = "^(\\+255|255|0)+(63|73)+[1-9][0-9]{6}";

        return phoneNumber.matches(regex);
    }

    public static boolean isValidTZNumber(String phoneNumber) {
        phoneNumber = phoneNumber.replaceAll("\\s+",""); // Clear spaces

        return phoneNumber.matches("^(\\+255|255|0)+([67])+[1-9]{2}+[0-9]{6}");
    }

    public static String getStandardTZNumber(String num) {
        String phoneNumber = num.replaceAll("\\s+",""); // Clear spaces

        String patternOne = "^(\\+255)+([67])+[1-9]{2}+[0-9]{6}";

        String patternTwo = "^(0)+([67])+[1-9]{2}+[0-9]{6}";

        String patternThree = "^(255)+([67])+[1-9]{2}+[0-9]{6}";

        String patternFour = "^([67])+[1-9]{2}+[0-9]{6}";

        if (phoneNumber.matches(patternOne)) {
            return phoneNumber;
        } else if (phoneNumber.matches(patternTwo)) {
            return "+255" + phoneNumber.substring(1);
        } else if (phoneNumber.matches(patternThree)) {
            return "+" + phoneNumber;
        } else if (phoneNumber.matches(patternFour)) {
            return "+255" + phoneNumber;
        }

        return phoneNumber;
    }
}