Left padding a String with Zeros [duplicate]

Question

This question already has an answer here:

• How can I pad a String in Java? 27 answers

I've seen similar questions here and here.

But am not getting how to left pad a String with Zero.

input: "129018" output: "0000129018"

The total output length should be TEN.

Answer 1

I have used this:

DecimalFormat numFormat = new DecimalFormat("00000");
System.out.println("Code format: "+numFormat.format(123));

Result: 00123

I hope you find it useful!

Answer 2

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 3

If you need performance and know the maximum size of the string use this:

String zeroPad = "0000000000000000";
String str0 = zeroPad.substring(str.length()) + str;

Be aware of the maximum string size. If it is bigger then the StringBuffer size, you'll get a java.lang.StringIndexOutOfBoundsException.

Answer 4

I prefer this code:

public final class StrMgr {

    public static String rightPad(String input, int length, String fill){                   
        String pad = input.trim() + String.format("%"+length+"s", "").replace(" ", fill);
        return pad.substring(0, length);              
    }       

    public static String leftPad(String input, int length, String fill){            
        String pad = String.format("%"+length+"s", "").replace(" ", fill) + input.trim();
        return pad.substring(pad.length() - length, pad.length());
    }
}

and then:

System.out.println(StrMgr.leftPad("hello", 20, "x")); 
System.out.println(StrMgr.rightPad("hello", 20, "x"));

Answer 5

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 6

This will pad left any string to a total width of 10 without worrying about parse errors:

String unpadded = "12345"; 
String padded = "##########".substring(unpadded.length()) + unpadded;

//unpadded is "12345"
//padded   is "#####12345"

If you want to pad right:

String unpadded = "12345"; 
String padded = unpadded + "##########".substring(unpadded.length());

//unpadded is "12345"
//padded   is "12345#####"  

You can replace the "#" characters with whatever character you would like to pad with, repeated the amount of times that you want the total width of the string to be. E.g. if you want to add zeros to the left so that the whole string is 15 characters long:

String unpadded = "12345"; 
String padded = "000000000000000".substring(unpadded.length()) + unpadded;

//unpadded is "12345"
//padded   is "000000000012345"  

The benefit of this over khachik's answer is that this does not use Integer.parseInt, which can throw an Exception (for example, if the number you want to pad is too large like 12147483647). The disadvantage is that if what you're padding is already an int, then you'll have to convert it to a String and back, which is undesirable.

So, if you know for sure that it's an int, khachik's answer works great. If not, then this is a possible strategy.