這樣也可以
public class TestString {
????public static void main(String[] args) {
????????// 創建一個空的StringBuilder對象
????????StringBuilder str = new StringBuilder();
????????// 追加字符串
????????str.append("jaewkjldfxmopzdmab");
????????// 從后往前每隔三位插入逗號
????????int num = str.length();
????????while (num>3) {
????????????num -= 3;
????????????str.insert(num, ",");
????????}
????????// 將StringBuilder對象轉化為String對象并打印
????????System.out.println(str.toString());
????}
}
2019-10-11
插入","以后，str.length().就改變了啊
2019-07-26
老哥，這個其實和for循環的思路是一樣的。
for(int?num?=?str.length()-3;?num?>=?0;?num?=?num-3?){? str.insert(num,','); }