classPrinter{void open(){System.out.println("open");}void close(){System.out.println("close");}void print(String s){System.out.println("print-->"+ s);}}classHPPrinter extends Printer{}classCanonPrinter extends Printer{void close(){this.clean(); super.close();}void clean(){System.out.println("clean");}}classTest{publicstaticvoid main(String args []){int flag =1;if(flag ==0){HPPrinter hpPrinter =newHPPrinter(); hpPrinter.open(); hpPrinter.print("abc"); hpPrinter.close();}elseif(flag ==1){CanonPrinter canonPrinter =newCanonPrinter(); canonPrinter.open(); canonPrinter.print("123"); canonPrinter.close();}}}原文：http://www.cnblogs.com/arroneve/p/5815445.html