Left padding a String with Zeros [duplicate]

Answer 1

An old question, but I also have two methods.

---

For a fixed (predefined) length:

    public static String fill(String text) {
        if (text.length() >= 10)
            return text;
        else
            return "0000000000".substring(text.length()) + text;
    }

---

For a variable length:

    public static String fill(String text, int size) {
        StringBuilder builder = new StringBuilder(text);
        while (builder.length() < size) {
            builder.append('0');
        }
        return builder.toString();
    }

Answer 2

    int number = -1;
    int holdingDigits = 7;
    System.out.println(String.format("%0"+ holdingDigits +"d", number));

Just asked this in an interview........

My answer below but this (mentioned above) is much nicer->

String.format("%05d", num);

My answer is:

static String leadingZeros(int num, int digitSize) {
    //test for capacity being too small.

    if (digitSize < String.valueOf(num).length()) {
        return "Error : you number  " + num + " is higher than the decimal system specified capacity of " + digitSize + " zeros.";

        //test for capacity will exactly hold the number.
    } else if (digitSize == String.valueOf(num).length()) {
        return String.valueOf(num);

        //else do something here to calculate if the digitSize will over flow the StringBuilder buffer java.lang.OutOfMemoryError 

        //else calculate and return string
    } else {
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < digitSize; i++) {
            sb.append("0");
        }
        sb.append(String.valueOf(num));
        return sb.substring(sb.length() - digitSize, sb.length());
    }
}

Answer 3

String paddedString = org.apache.commons.lang.StringUtils.leftPad("129018", 10, "0")

the second parameter is the desired output length

"0" is the padding char

Answer 4

Use Google Guava:

Maven:

<dependency>
     <artifactId>guava</artifactId>
     <groupId>com.google.guava</groupId>
     <version>14.0.1</version>
</dependency>

Sample code:

Strings.padStart("129018", 10, '0') returns "0000129018"  

Answer 5

Here's another approach:

int pad = 4;
char[] temp = (new String(new char[pad]) + "129018").toCharArray()
Arrays.fill(temp, 0, pad, '0');
System.out.println(temp)

Answer 6

Right padding with fix length-10: String.format("%1$-10s", "abc") Left padding with fix length-10: String.format("%1$10s", "abc")