What is my error? (MyString)

Question

public my string substring( int beginIndex){
char []substr= new char [ this.length () - beginIndex];
for (int i = beginIndex ; i <this.length () i++); {
substr [i - beginIndex] = this.charAt (i);
}
return MyString (substr);
}

Answer 1

Is the error you're getting "String cannot be converted to char[]" ?
You can use the String.valueOf() method to convert it.
so:
public String subString(..){

..... // other code here
// remove your return
return String.valueOf(substr);
}