现有publicclassDemo{publicstaticvoidmain(String[]args){Listal=newArrayList();a1.add("
现有publicclassDemo{publicstaticvoidmain(String[]args){Listal=newArrayList();a1.add("l");a1.add("2");a1.add("2");a1.add("3");System.out.println(al);}}上述程序执行后的输出是哪项?()
A、[1,2,3]
B、[1,2,3,3]
C、[1,2,2,3]
D、[2,1,3,2]