截取带有中文的字符串

public class GetString {
public static String getString(String str,int
len) {
String temp = ""; // 存取截取字符串
int count = 0;
boolean flag = false; // 标记char状态
byte[] b = str.getBytes();
if (len > str.length()) {
return str;
}

for (int i = 0; i < len; i++) {
if (b[i] < 0 && !flag) {
flag = true;
count += 1;
} else {
count = i + 1;
flag = false;
}
temp = str.substring(0, count);
}
System.out.println(str);// 原字符串
System.out.println(temp);
return temp;
}

public static void main(String[] args) {
String str = "abc我中国sg们w";
getString(str, 4);
}