Format a string with leading zeros in Java

This post will discuss how to format a string with leading zeros in Java.

1. Using `String.format()` method

The standard solution to format a string is to use the String.format() method, which takes printf-style format strings. To get a zero-padded string, you can use the '0' flag with width indicating the minimum number of characters to be written to the output.

public class Main {

public static void main(String[] args) {

String str = "1011101";

int width = 16;

String formatted = String.format("%0" + width + "d", Integer.valueOf(str));

System.out.println(formatted);

}

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Output:

0000000001011101

2. Using Apache Commons Lang

Apache Commons Lang StringUtils utility class provides the leftPad() method that can left-pad a string with the specified character. You can use it as follows:

import org.apache.commons.lang3.StringUtils;

public class Main {

public static void main(String[] args) {

String str = "1011101";

int size = 16;

char padChar = '0';

String formatted = StringUtils.leftPad(str, size, padChar);

System.out.println(formatted);

}

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Output:

0000000001011101

3. Using Guava Libaray

Guava’ Strings utility class provides the padStart() method that prepends a String with copies of the specified character to reach the specified length. You can use it as follows:

import com.google.common.base.Strings;

public class Main {

public static void main(String[] args) {

String str = "1011101";

int minLength = 16;

char padChar = '0';

String formatted = Strings.padStart(str, minLength, '0');

System.out.println(formatted);

}

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Output:

0000000001011101

That’s all about formatting a string with leading zeros in Java.

Format a string with leading zeros in Java

1. Using String.format() method

2. Using Apache Commons Lang

3. Using Guava Libaray

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1. Using `String.format()` method