How to format a Java string with leading zero? [duplicate]
Here is the String, for example:
"Apple"
and I would like to add zero to fill in 8 chars:
"000Apple"
How can I do so?
public class LeadingZerosExample {
public static void main(String[] args) {
int number = 1500;
// String format below will add leading zeros (the %0 syntax)
// to the number above.
// The length of the formatted string will be 7 characters.
String formatted = String.format("%07d", number);
System.out.println("Number with leading zeros: " + formatted);
}
}
In case you have to do it without the help of a library:
("00000000" + "Apple").substring("Apple".length())
(Works, as long as your String isn't longer than 8 chars.)
StringUtils.leftPad(yourString, 8, '0');
This is from commons-lang. See javadoc
This is what he was really asking for I believe:
String.format("%0"+ (8 - "Apple".length() )+"d%s",0 ,"Apple");
output:
000Apple
You can use the String.format method as used in another answer to generate a string of 0's,
String.format("%0"+length+"d",0)
This can be applied to your problem by dynamically adjusting the number of leading 0's in a format string:
public String leadingZeros(String s, int length) {
if (s.length() >= length) return s;
else return String.format("%0" + (length-s.length()) + "d%s", 0, s);
}
It's still a messy solution, but has the advantage that you can specify the total length of the resulting string using an integer argument.
You can use this:
org.apache.commons.lang.StringUtils.leftPad("Apple", 8, "0")
Using Guava's Strings
utility class:
Strings.padStart("Apple", 8, '0');
I've been in a similar situation and I used this; It is quite concise and you don't have to deal with length or another library.
String str = String.format("%8s","Apple");
str = str.replace(' ','0');
Simple and neat. String format returns " Apple"
so after replacing space with zeros, it gives the desired result.
String input = "Apple";
StringBuffer buf = new StringBuffer(input);
while (buf.length() < 8) {
buf.insert(0, '0');
}
String output = buf.toString();
Use Apache Commons StringUtils.leftPad (or look at the code to make your own function).
You can use:
String.format("%08d", "Apple");
It seems to be the simplest method and there is no need of any external library.
In Java:
String zeroes="00000000";
String apple="apple";
String result=zeroes.substring(apple.length(),zeroes.length())+apple;
In Scala:
"Apple".foldLeft("00000000"){(ac,e)=>ac.tail+e}
You can also explore a way in Java 8 to do it using streams and reduce (similar to the way I did it with Scala). It's a bit different to all the other solutions and I particularly like it a lot.
I like the solution from Pad a String with Zeros
String.format("%1$" + length + "s", inputString).replace(' ', '0');
with length = "8" and inputString = "Apple"
public class PaddingLeft {
public static void main(String[] args) {
String input = "Apple";
String result = "00000000" + input;
int length = result.length();
result = result.substring(length - 8, length);
System.out.println(result);
}
}
You may have to take care of edgecase. This is a generic method.
public class Test {
public static void main(String[] args){
System.out.println(padCharacter("0",8,"hello"));
}
public static String padCharacter(String c, int num, String str){
for(int i=0;i<=num-str.length()+1;i++){str = c+str;}
return str;
}
}
public static void main(String[] args)
{
String stringForTest = "Apple";
int requiredLengthAfterPadding = 8;
int inputStringLengh = stringForTest.length();
int diff = requiredLengthAfterPadding - inputStringLengh;
if (inputStringLengh < requiredLengthAfterPadding)
{
stringForTest = new String(new char[diff]).replace("\0", "0")+ stringForTest;
}
System.out.println(stringForTest);
}
public static String lpad(String str, int requiredLength, char padChar) {
if (str.length() > requiredLength) {
return str;
} else {
return new String(new char[requiredLength - str.length()]).replace('\0', padChar) + str;
}
}
Did anyone tried this pure Java solution (without SpringUtils):
//decimal to hex string 1=> 01, 10=>0A,..
String.format("%1$2s", Integer.toString(1,16) ).replace(" ","0");
//reply to original question, string with leading zeros.
//first generates a 10 char long string with leading spaces, and then spaces are
//replaced by a zero string.
String.format("%1$10s", "mystring" ).replace(" ","0");
Unfortunately this solution works only if you do not have blank spaces in a string.
Solution with method String::repeat (Java 11)
String str = "Apple";
String formatted = "0".repeat(8 - str.length()) + str;
If needed change 8 to another number or parameterize it
This is fast & works for whatever length.
public static String prefixZeros(String value, int len) {
char[] t = new char[len];
int l = value.length();
int k = len-l;
for(int i=0;i<k;i++) { t[i]='0'; }
value.getChars(0, l, t, k);
return new String(t);
}
Can be faster then Chris Lercher answer when most of in String have exacly 8 char
int length = in.length();
return length == 8 ? in : ("00000000" + in).substring(length);
in my case on my machine 1/8 faster.
Here is the simple API-less "readable script" version I use for pre-padding a string. (Simple, Readable, and Adjustable).
while(str.length() < desired_length)
str = '0'+str;
If you want to write the program in pure Java you can follow the below method or there are many String Utils to help you better with more advanced features.
Using a simple static method you can achieve this as below.
public static String addLeadingText(int length, String pad, String value) {
String text = value;
for (int x = 0; x < length - value.length(); x++) text = pad + text;
return text;
}
You can use the above method addLeadingText(length, padding text, your text)
addLeadingText(8, "0", "Apple");
The output would be 000Apple
It isn't pretty, but it works. If you have access apache commons i would suggest that use that
if (val.length() < 8) {
for (int i = 0; i < val - 8; i++) {
val = "0" + val;
}
}
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