code: public void setDigitStrings(String[] digitStrings) {
          if (digitStrings == null) {
              throw new NullPointerException("The input digit string array is null");
          }
          if (digitStrings.length != 10) {
              throw new IllegalArgumentException("Number of digit strings is not 10");
          }
  
          // Scan input array and create char[] representation if possible
          String[] tmpDigitStrings = new String[10];
          char[] tmpDigits = new char[10];
          for (int i = 0; i < 10; i++) {
              if (digitStrings[i] == null) {
                  throw new IllegalArgumentException("The input digit string array contains a null element");
              }
              tmpDigitStrings[i] = digitStrings[i];
              if (tmpDigits != null && digitStrings[i].length() == 1) {
                  tmpDigits[i] = digitStrings[i].charAt(0);
              } else {
                  // contains digit string with multiple UTF-16 code units
                  tmpDigits = null;
              }
          }
  
          this.digitStrings = tmpDigitStrings;
  
          if (tmpDigits == null) {
              // fallback to the default digit chars
              this.zeroDigit = DEF_DIGIT_CHARS_ARRAY[0];
              this.digits = DEF_DIGIT_CHARS_ARRAY;
          } else {
              this.zeroDigit = tmpDigits[0];
              this.digits = tmpDigits;
          }
      }
docs: <strong>[icu]</strong> Sets the array of strings used as digits, in order from 0 through 9
  <p>
  <b>Note:</b>
  <p>
  When the input array of digit strings contains any strings
  represented by multiple Java chars, then {@link #getDigits()} will return
  the default digits ('0' - '9') and {@link #getZeroDigit()} will return the
  default zero digit ('0').
  
  @param digitStrings The array of digit strings. The length of the array must be exactly 10.
  @throws NullPointerException if the <code>digitStrings</code> is null.
  @throws IllegalArgumentException if the length of the array is not 10.
  @see #getDigitStrings()
  @hide draft / provisional / internal are hidden on Android