口试截取字符串出现半个汉字乱码

面试截取字符串出现半个汉字乱码

String str="我ABC汉";//7
???? int bn=6;//要截取的字节数
???? int a=0;//字节数
??StringBuffer sb=new StringBuffer();
??
??for(int i=0;i<str.length();i++)
??{
???char c=str.charAt(i);
???boolean flag=isChanese(c);
???if(flag)
???{
????a=a+2;
???}
???else{
????? a++;
???}
???if(a<=bn)
???{
????sb.append(c);
???}
???
??}
??System.out.println(sb.toString());
??
??? ?

??? }
??? //判断是汉字还是字符
??? public static? boolean isChanese(char c)
??? {
??? ?byte[] b=(c+"").getBytes();
??? ?if(b.length==2)
??? ?{
??? ??return true;
??? ?}
??? ?return false;
??? }