Java NullPointerException in Array

specialConsonants and specialConsonantsUni are not initilized. You've just defined setSpecial() but not called it before doing replaces

The correct behavior would be:

public static void main(String args[]){
    setSpecial();
    for (int i=0; i < specialConsonants.length; i++){
        text = text.replace(specialConsonants[i], specialConsonantsUni[i]);
        System.out.println(text);
    }
}

note also that setSpecial should be static in that case

Moreover you have to change dimension of specialConsonants to 6

Because specialConsonants[i] is null. You have not initialized it.

its like

specialConsonants = {null,null,null,null}

You need to make function setSpecial static then call it before the loop.

public static String[] specialConsonants = new String[4];

public void setSpecial(){
    // ...
    specialConsonants[5] = "/\\r/g";
}

specialConsonants is of array size 4. There is no 5th index for it. Also you haven't called the array initializer method.

You're adding elements to an already filled array. Array indexes start from 0, When you declared :

 public static String[] specialConsonants = new String[4];

That means you can only use specialConsonants[0] to specialConsonants[3]

I suggest you use a hashmap for this thing.

HashMap<String, String> specialConsonants = new HashMap<String, String>();
....
specialConsonants.put("ං" , "ng" );
....

You've declared specialConsonants as an array of length 4, but you're assigning 6 elements to it.

specialConsonants[4] has enough room for elements 0, 1, 2, and 3. You need to declare it as specialConsonants[6] if you want indices 0 - 5.

Then you need to call setSpecial() before you use the array in your loop.

the array definition looks wrong, seems you want two same size array but you defined as :

public static String[] specialConsonants = new String[4];
public static String[] specialConsonantsUni = new String[6];

I think it should be:

public static String[] specialConsonants = new String[6];
public static String[] specialConsonantsUni = new String[6];