question: public static String newString ( int [ ] codePoints , int offset , int count ) { if ( count < 0 ) { throw new IllegalArgumentException ( ) ; } char [ ] chars = new char [ count ] ; int w = 0 ; for ( int r = offset , e = offset + count ; r < e ; ++ r ) { int cp = codePoints [ r ] ; if ( cp < 0 || cp > 0x10ffff ) { throw new IllegalArgumentException ( ) ; } while ( true ) { try { if ( cp < 0x010000 ) { chars [ w ] = ( char ) cp ; w ++ ; } else { chars [ w ] = ( char ) ( LEAD_SURROGATE_OFFSET_ + ( cp > > LEAD_SURROGATE_SHIFT_ ) ) ; chars [ w + 1 ] = ( char ) ( TRAIL_SURROGATE_MIN_VALUE + ( cp & TRAIL_SURROGATE_MASK_ ) ) ; w += 2 ; } break ; } catch ( IndexOutOfBoundsException ex ) { int newlen = ( int ) ( Math . ceil ( ( double ) codePoints . length * ( w + 2 ) / ( r - offset + 1 ) ) ) ; char [ ] temp = new char [ newlen ] ; System . arraycopy ( chars , 0 , temp , 0 , w ) ; chars = temp ; } } } return new String ( chars , 0 , w ) ; }
target:  Cover JDK 1.5 API. Create a String from an array of codePoints.