How to implement java string formatting and add 0 if the length is insufficient

You can fill in the number of digits with one line of code, but if you can fill in the number of digits with one line of code, you need to fill in spaces in front of it, and if you want to fill in 0, you need an integer type, use The function you get is String.format, which can format integers, strings, dates, etc.

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For example:

System.out.println(String.format(“%09d”, 123);

Output: 000000123

System.out.println(String.format(“%9s”, “123″);

Output: 123

The code is as follows:

System.out.println(String.format(“%09d”, Long.parseLong(“123″)));

Output: 000000123

The example code is as follows:

public static String addZeroForNum(String str, int strLength) {
    int strLen = str.length();
    if (strLen < strLength) {
        while (strLen < strLength) {
            StringBuffer sb = new StringBuffer();
            sb.append("0").append(str);// 左补0
            // sb.append(str).append("0");//右补0
            str = sb.toString();
            strLen = str.length();
        }
    }
    return str;
}

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