How to Preserve Leading Zeros When Converting Byte Arrays to Hex Strings in Java?

Preserving Leading Zeros When Converting Byte Arrays to Hex Strings in Java

To convert a byte array to a hexadecimal digit string while maintaining leading zeros in Java, implement the following approaches:

Using String.format

Format each byte as a fixed-width two-character hexadecimal string using String.format. Leading zeros are guaranteed:

byte[] bytes = ...;
String hexString = "";
for (byte b : bytes) {
    hexString += String.format("%02X", b);
}

Using Apache Commons Codec

Take advantage of Apache Commons Codec's Hex.encodeHexString method:

import org.apache.commons.codec.binary.Hex;

byte[] bytes = ...;
String hexString = Hex.encodeHexString(bytes);

Using Guava's ByteString

Employ Guava's ByteString class to convert the bytes to a hex string:

import com.google.common.hash.Hashing;

byte[] bytes = ...;
String hexString = Hashing.sha256().hashBytes(bytes).toString();

Each approach ensures that leading zeros are preserved when converting byte arrays to hex strings.

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