下面的程序段运行结果为_______。public class ExampleStringBuffer { public static void main(String args[]){ StringBuffer sb=new StringBuffer("test"); System.out.println("length="+sb.length()); System.out.println("charAt="+sb.charAt(3));
A.length=20 charAt=t B.length=20 charAt=s C.length=4 charAt=s D.length=4 charAt=t