question: private static final boolean isHeaderEnd ( StringBuilder sb ) { int len = sb . length ( ) ; if ( len > 2 ) { if ( LF2 . equals ( sb . substring ( len - 2 ) ) ) { return true ; } } if ( len > 4 ) { if ( CRLF2 . equals ( sb . substring ( len - 4 ) ) ) { return true ; } } return false ; }
target:  Check if the current StringBuilder trailing characters is an HTTP header end (empty CRLF).