Java – バイトを16進数に変換する方法

投稿日: 2019-11-05 2019-11-05
タグ: bytes, hashing, hex, sha256

Javaでは、 `String.format（”％02x “、bytes）`を使ってバイトを簡単に16進数に変換することができます。

    private static String bytesToHex(byte[]hashInBytes) {

        StringBuilder sb = new StringBuilder();
        for (byte b : hashInBytes) {
            sb.append(String.format("%02x", b));
        }
        return sb.toString();

    }

代替ソリューション。

    private static String bytesToHex1(byte[]hashInBytes) {

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < hashInBytes.length; i++) {
            sb.append(Integer.toString((hashInBytes[i]& 0xff) + 0x100, 16).substring(1));
        }
        return sb.toString();

    }

    private static String bytesToHex2(byte[]hashInBytes) {

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < hashInBytes.length; i++) {
            String hex = Integer.toHexString(0xff & hashInBytes[i]);
            if (hex.length() == 1) sb.append('0');
            sb.append(hex);
        }
        return sb.toString();

    }

1. 16進数のバイト – SHA-256

SHA-256アルゴリズムを使用してパスワードをハッシュするJavaの完全な例。

ByesToHex.java

package com.mkyong.hashing;

import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

public class ByesToHex {

    public static void main(String[]args) throws NoSuchAlgorithmException {

        String password = "123456";

        MessageDigest md = MessageDigest.getInstance("SHA-256");

        byte[]hashInBytes = md.digest(password.getBytes(StandardCharsets.UTF__8));

        System.out.println(bytesToHex(hashInBytes));
        System.out.println(bytesToHex2(hashInBytes));
        System.out.println(bytesToHex3(hashInBytes));

    }

    private static String bytesToHex(byte[]hashInBytes) {

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < hashInBytes.length; i++) {
            sb.append(Integer.toString((hashInBytes[i]& 0xff) + 0x100, 16).substring(1));
        }
        return sb.toString();

    }

    private static String bytesToHex2(byte[]hashInBytes) {

        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < hashInBytes.length; i++) {
            String hex = Integer.toHexString(0xff & hashInBytes[i]);
            if (hex.length() == 1) sb.append('0');
            sb.append(hex);
        }
        return sb.toString();

    }

    private static String bytesToHex3(byte[]hashInBytes) {

        StringBuilder sb = new StringBuilder();
        for (byte b : hashInBytes) {
            sb.append(String.format("%02x", b));
        }
        return sb.toString();

    }

}

出力

8d969eef6ecad3c29a3a629280e686cf0c3f5d5a86aff3ca12020c923adc6c92
8d969eef6ecad3c29a3a629280e686cf0c3f5d5a86aff3ca12020c923adc6c92
8d969eef6ecad3c29a3a629280e686cf0c3f5d5a86aff3ca12020c923adc6c92