StringBuffer输出

public class Test {
public static void main(String[] args) {
    StringBuffer a = new StringBuffer("A");
    StringBuffer b = new StringBuffer("B");
    operator(a, b);
    System.out.println(a + "," + b);
}
public static void operator(StringBuffer x, StringBuffer y) {
    x.append(y); y = x;
}
}

输出结果：

AB,B