question: public String replace ( char oldChar , char newChar ) { int index = indexOf ( oldChar , 0 ) ; if ( index == - 1 ) { return this ; } char [ ] buffer = new char [ count ] ; System . arraycopy ( value , offset , buffer , 0 , count ) ; do { buffer [ index ++ ] = newChar ; } while ( ( index = indexOf ( oldChar , index ) ) != - 1 ) ; return new String ( 0 , count , buffer ) ; }
target:  Copies this String replacing occurrences of the specified character with another character.