java String字符串空格隔开

public class StringTest {

public static void main(String[] args) {

String str = "1234567890123";
String stri = spaceAt4(str);
System.out.println(stri);
//结果：1234 5678 9012 3
}

public static String spaceAt4(String str) {

StringBuilder sb = new StringBuilder();
int length = str.length();
for (int i = 0; i < length; i += 4) {
if (length - i <= 8) {      //防止ArrayIndexOutOfBoundsException
sb.append(str.substring(i, i + 4)).append(" ");
sb.append(str.substring(i + 4));
break;
}
sb.append(str.substring(i, i + 4)).append(" ");
}

return sb.toString();
}

}