JAVA传参的问题

public class Test1{ static void swap(StringBuffer a,StringBuffer b) {  a.append(" more");  b=a; } public static void main(String args[]) {  StringBuffer a=new StringBuffer("One");  StringBuffer b=new StringBuffer("Two");  swap(a,b);  System.out.println("a is "+a+"\nb is "+b); }}

?

OneTwo,Two
OneTwo,OneTwo
?