在写课程实验时遇到了给节点label增加序号的问题。这就需要补全高位的0。
这里用到了String.format()方法。
String类的format()方法用于创建格式化的字符串以及连接多个字符串对象。
String Label = "label";
String newLabel = String.format("%s%03d", Label, 7);//0是前面补全0的标志，3是位数
System.out.println(newLabel);
输出：
label007
同时String.format()方法还有许多种用法
下表总结了String.format()方法支持的标志。y表示该标志对于指定的参数类型是受支持的。
| Flag | General | Character | Integral | Floating Point | Date/Time | Description |
|---|---|---|---|---|---|---|
| '-' | y | y | y | y | y | The result will be left-justified. |
| '#' | y1 | - | y3 | y | - | The result should use a conversion-dependent alternate form |
| '+' | - | - | y4 | y | - | The result will always include a sign |
| ' ' | - | - | y4 | y | - | The result will include a leading space for positive values |
| '0' | - | - | y | y | - | The result will be zero-padded |
| ',' | - | - | y2 | y5 | - | The result will include locale-specific grouping separators |
| '(' | - | - | y4 | y5 | - | The result will enclose negative numbers in parentheses |
1 Depends on the definition of Formattable.
2 For 'd' conversion only.
3 For 'o', 'x', and 'X' conversions only.
4 For 'd', 'o', 'x', and 'X' conversions applied to BigInteger or 'd' applied to byte, Byte, short, Short, int and Integer, long, and Long.
5 For 'e', 'E', 'f', 'g', and 'G' conversions only.
具体用法见 Class Formatter