I'd suggest adding a comment mentioning how the order of values in the arrays `morseChar` and `morseNumber` are important for the conversion.

At first glance I was confused how the conversion was being done.

You should declare `morseChar` and `morseNumber` as final class variables so they are easily visible & can be used in other methods.

If you may add symbols to the code, a class or enum containing the MorseCode and english character can be added. This also makes the opposite conversion very easy.

     // Note: Simply add numbers and symbols to this enum. 
     // The Order does not matters.
     public enum MorseCharacter
     {
         A(".-", 'a'),
         B("-...", 'b'),
         C("-.-.", 'c'),
         D("-..", 'd'),
         E(".", 'e'),
         F("..-.", 'f'),
         G("--.", 'g'),
         H("....", 'h'),
         I("..", 'i'),
         J(".---", 'j'),
         K("-.-", 'k'),
         L(".-..", 'l'),
         M("--", 'm'),
         N("-.", 'n'),
         O("---", 'o'),
         P(".--.", 'p'),
         Q("--.-", 'q'),
         R(".-.", 'r'),
         S("...", 's'),
         T("-", 't'),
         U("..-", 'u'),
         V("...-", 'v'),
         W(".--", 'w'),
         X("-..-", 'x'),
         Y("-.--", 'y'),
         Z("--..", 'z');
    
         private final String morseCode;
         private final char character;
         private static final MorseCharacter[] ALL_VALUES = values();
    
         MorseCharacter(String morseCode, char character)
         {
             this.morseCode = morseCode;
             this.character = character;
         }
    
         public String getMorseCode()
         {
             return morseCode;
         }
    
         public char getCharacter()
         {
             return character;
         }
    
         public static MorseCharacter valueOf(char character)
         {
             for (MorseCharacter morseChar : ALL_VALUES)
             {
                 if (morseChar.getCharacter() == character)
                 {
                     return morseChar;
                 }
             }
    
             throw new RuntimeException("Morse character not found: " + character);
         }
     }
    
     public static String toMorse(String text) 
     {
         String morseText = "";
         text = text.toLowerCase();
    
         for (int i = 0; i < text.length(); i++) 
         {
             morseText += MorseCharacter.valueOf(text.charAt(i)).getMorseCode();
         }
         return morseText;
     }