java.lang.String concat() tweak:

Java Doc says
   
        Concatenation happens  the specified string to the end of this string.

If the length of the argument string is 0, then this String object is returned. Otherwise, a new String object is created, representing a character sequence that is the concatenation of the character sequence represented by this String object and the character sequence represented by the argument string.

Saying that , how to implement our own concat().

Here is the sample:

 public static void concat(String firstString ,String secondString){

char [] firstStringarray = firstString.toCharArray();

char [] secondStringarray = secondString.toCharArray();

if(secondStringarray.length == 0){

System.out.println(firstString);

}else

{

       char [] newArray = new char[firstStringarray.length +                                       secondStringarray.length];

int index = 0;

while(index < firstStringarray.length){

newArray[index] = firstStringarray[index];

index ++;

}

while(index < newArray.length){

newArray[index] =         secondStringarray[secondStringarray.length - (newArray.length - index)];                                 

index ++;

}

Sytem.out.println(new String(newArray));

}

}