Java int to string with zeros

How to convert an integer to a string in Java

There are many ways to convert an integer value (primitive int or an Integer object) into a string in Java. Unlike string to integer conversion, converting an integer to a string is a simple operation.

The toString() method is the most common method provided by every Java object that returns a string representation of the object. It can be used as a static method of the Integer class to convert a primitive int value into a string:

int number = 2344; String str = Integer.toString(number); System.out.println(str); // 2344 

If the integer variable is already an instance of Integer (wrapper class of primitive int ), there is no need to use the static method. It is better to call its toString() method:

Integer number = 2344; String str = number.toString(); System.out.println(str); // 2344 

The valueOf() method is a static method of the String class that accepts multiple data types like int , long , double , boolean , char , and Object , and returns its string representation:

int number = 2344; String str = String.valueOf(number); System.out.println(str); // 2344 

Internally, it calls the toString() method of the corresponding wrapper of the primitive value. For example, in the case of an integer, it calls the Integer.toString() method to perform the conversion. Therefore, it is better to use the Integer.toString() method.

Both StringBuildeer and StringBuffer are commonly used to concatenate different values into a single String object using the append() method. Here is an example that uses the StringBuilder class to convert an integer into a string:

int number = 2344; StringBuilder builder = new StringBuilder(); builder.append(number); String str = builder.toString(); System.out.println(str); // 2344 

The StringBuilder class is not thread-safe but is faster, whereas the StringBuffer is thread-safe but slower.

The String.format() method returns a formatted string using the specified format string and arguments. While this method is not meant to convert but rather format a string, it can be used to convert an integer to a string by using the %d format:

int number = 2344; String str = String.format("%d", number); System.out.println(str); // 2344 

// Text width String.format("|%10d|", 123); // | 123| // Justify left String.format("|%-10d|", 123); // |123 | // Pad with zeros String.format("|%010d|", 123); // |0000000123| // Positive number String.format("%+d", 123); // +123 // Thousands separator String.format("%,d", 1234567); // 1,234,567 // Enclose -ve number with parenthesis String.format("%o", 123); // (123) 

Finally, the last approach to convert an integer to a string is using string concatenation. Again, this is not the recommended way, as concatenation is not meant for conversion. When you concatenate an integer value with a string, the result is also a string:

int number = 2344; String str = "" + number; System.out.println(str); // 2344 

Converting an integer value into a string is one of the most common operations in Java. In this article, we have covered 5 different ways to achieve this. The rule of thumb is if the integer variable is a primitive int value, it is better to use the Integer.toString() or String.vaueOf() method. However, if the variable is already an instance of wrapper class Integer , there is no need to reinvent the wheel. Instead, call the toString() method of the Integer object to get a string representation of the value. Read this guide to learn about other data type conversions like string to date, a string to float, a string to double, and more in Java. ✌️ Like this article? Follow me on Twitter and LinkedIn. You can also subscribe to RSS Feed.

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How to Add Leading Zeros to Integers in Java ? String Left Padding Example Program

Hello guys, you may know that from Java 5 onwards it’s easy to left pad Integers with leading zeros when printing number as String. In fact, You can use the same technique to left and right pad Java String with any characters including zeros, space. Java 5 provides String format methods to display String in various formats. By using the format() method we can add leading zeros to an Integer or String number. By the way, this is also known as left padding Integers with zero in Java. For those who are not familiar with the left and right padding of String, here is a quick recap;

When we add characters like zero or space on left of a String, its known as left padding and when we do the same on the right side of String, it’s known as right padding of String. This is useful when you are displaying currency amounts or numbers, which has fixed width, and you want to add leading zeros instead of space in front of Integers.

If by any chance, You are not using Java 5 or you like to use open source projects like Apache commons, Google Guava or Spring framework then you can use leftPad() and rightPad() methods provided by StringUtils class. I personally prefer JDK function if it provides required functionality but It’s very common to have Spring , Apache commons or Guava already in your classpath.

In that case use those method because they are more convenient, readable and you don’t need to remember different String formatting options to left and right pad a String with zero or any character . By the way, while padding String and number left and right, it’s worth remember not to right pad numbers with zero, it will completely change there meaning.

Left and Right padding Integer and String in Java

In this Java tutorial, we will see How to add leading zero to Integer or String in Java. Both are actually same because you only print String in Java and left padding is done at the time of display and the original Integer value is not affected. The format() method of String class in Java 5 is the first choice. You just need to add «%03d» to add 3 leading zeros in an Integer. Formatting instruction to String starts with «%» and 0 is the character which is used in padding. By default left padding is used, 3 is the size and d is used to print integers.

It means if the number has 1 or 2 digits than some leading zeros will be added to the number to make its width equal to 3. This is also known as left padding of Integers in Java. By default Java left pad with space and if you add 0 then Integer will be left padded with zero. You can not use other character e.g. # here.

On the other hand both Spring and Apache commons StringUtils provides you convenient leftPad() and rightPad() method to add left and right padding on String in Java. These methods also allow you to pass any character of your choice to be used as padding e.g. zero, # or space.

Java String left and right padding example

Let’s see some code example of left and right padding String and Integer in Java using Spring, Apache Commons StringUtils and format method of String.

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How to format a Java string with leading zero?

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.)

Solution 2

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); >> 

Solution 3

 StringUtils.leftPad(yourString, 8, '0'); 

Solution 4

This is what he was really asking for I believe:

String.format("%0"+ (8 - "Apple".length() )+"d%s",0 ,"Apple"); 

Solution 5

You can use the String.format method as used in another answer to generate a string of 0’s,

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.

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Comments

The -1 is probably because this is a not so good example: you’re using «magic numbers» and are concatenating Strings, something that should be replaced by using a StringBuilder or StringBuffer.

Even if you are not able to use commons-lang, you can easily copy the source from StringUtils to make your own function. That would be a much better general solution than the selected answer. docjar.com/html/api/org/apache/commons/lang/…

what if that would be the only method the library is used for? Perhaps the added library is even many times bigger than the app it is used in. I can imagine quite some reasons not to add a commons library in an application. Don’t get me wrong: I agree, it contains very useful stuff, but I understand the reluctance to stuff an app full of external JARs if the benefit is not needing to write just one (or a couple) of methods.

@kaliatech: yes, a much better GENERAL solution, but if he don’t want to use the library probably a focused (short) solution is more appropriate.

That’s pretty clever — but it took me about 30 seconds to «get it». I think a more readable solution would be better.

This is an -excellent- solution when you are embedding software on something without much space and the extra libraries just aren’t an option. Thanks!!

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Java Int Convert integer to string with left zero fill.

The integer converted to a string with enough leading zeros to fill the specified field width.

//package com.java2s; /* Please see the license information at the end of this file. */ public class Main < /** Convert integer to string with left zero fill. */* w w w . d e mo 2 s . c o m*/ * @param intValue The integer to convert. * @param width Width of result field. * * @return The integer converted to a string * with enough leading zeros to fill * the specified field width. */ public static String intToStringWithZeroFill(int intValue, int width) < String s = new Integer(intValue).toString(); if (s.length() < width) s = dupl('0', width - s.length()) + s; return s; > /** Duplicate character into string. * * @param ch The character to be duplicated. * @param n The number of duplicates desired. * * @return String containing "n" copies of "ch". * * * if n  */ public static String dupl(char ch, int n) < if (n > 0) < StringBuffer result = new StringBuffer(n); for (int i = 0; i < n; i++) < result.append(ch); >return result.toString(); > else < return ""; > > /** Duplicate string into string. * * @param s The string to be duplicated. * @param n The number of duplicates desired. * * @return String containing "n" copies of "s". * * * if n  */ public static String dupl(String s, int n) < if (n > 0) < StringBuffer result = new StringBuffer(n); for (int i = 0; i < n; i++) < result.append(s); >return result.toString(); > else < return ""; > > >

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