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<!DOCTYPE html>
<html lang="en">
<head>
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<title>HexFormat | java.evolved</title>
<meta name="description" content="Convert between hex strings and byte arrays with HexFormat.">
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<a href="/" class="logo">java.<span>evolved</span></a>
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<path d="M10 3C6.13 3 3 6.13 3 10c0 3.09 2 5.71 4.77 6.63.35.06.48-.15.48-.33v-1.16c-1.95.42-2.36-1.07-2.36-1.07-.32-.81-.78-1.03-.78-1.03-.64-.43.05-.42.05-.42.7.05 1.07.72 1.07.72.63 1.08 1.65.77 2.05.59.06-.46.24-.77.44-.95-1.57-.18-3.22-.78-3.22-3.48 0-.77.27-1.4.72-1.89-.07-.18-.31-.9.07-1.87 0 0 .59-.19 1.93.72.56-.16 1.16-.24 1.76-.24s1.2.08 1.76.24c1.34-.91 1.93-.72 1.93-.72.38.97.14 1.69.07 1.87.45.49.72 1.12.72 1.89 0 2.71-1.65 3.3-3.23 3.47.25.22.48.65.48 1.31v1.94c0 .19.13.4.48.33C15 15.71 17 13.09 17 10c0-3.87-3.13-7-7-7z"/>
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<a href="/" class="back-link">← All patterns</a>
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<a href="/math-clamp.html" aria-label="Previous pattern">←</a>
<a href="/pem-encoding.html" aria-label="Next pattern">→</a>
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<div class="breadcrumb">
<a href="/">Home</a>
<span class="sep">/</span>
<a href="/?cat=datetime">Date/Time</a>
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<span>HexFormat</span>
</div>
<div class="tip-header">
<div class="tip-meta">
<span class="badge datetime">Date/Time</span>
<span class="badge intermediate">intermediate</span>
</div>
<h1>HexFormat</h1>
<p>Convert between hex strings and byte arrays with HexFormat.</p>
</div>
<section class="compare-section">
<div class="section-label">Code Comparison</div>
<div class="compare-container">
<div class="compare-panel old-panel">
<div class="compare-panel-header">
<span class="compare-tag old">✕ Java 8</span>
<button class="copy-btn" data-code="old">Copy</button>
</div>
<div class="compare-code">
<pre class="code-text">// Pad to 2 digits, uppercase
String hex = String.format(
"%02X", byteValue);
// Parse hex string
int val = Integer.parseInt(
"FF", 16);</pre>
</div>
</div>
<div class="compare-panel modern-panel">
<div class="compare-panel-header">
<span class="compare-tag modern">✓ Java 17+</span>
<button class="copy-btn" data-code="modern">Copy</button>
</div>
<div class="compare-code">
<pre class="code-text">HexFormat hex = HexFormat.of()
.withUpperCase();
String s = hex.toHexDigits(
byteValue);
byte[] bytes =
hex.parseHex("48656C6C6F");</pre>
</div>
</div>
</div>
</section>
<section class="why-section">
<div class="section-label">Why the modern way wins</div>
<div class="why-grid">
<div class="why-card">
<div class="why-icon">📐</div>
<h3>Bidirectional</h3>
<p>Convert bytes→hex and hex→bytes with one API.</p>
</div>
<div class="why-card">
<div class="why-icon">🔧</div>
<h3>Configurable</h3>
<p>Delimiters, prefix, suffix, upper/lower case.</p>
</div>
<div class="why-card">
<div class="why-icon">📦</div>
<h3>Array support</h3>
<p>Encode/decode entire byte arrays at once.</p>
</div>
</div>
</section>
<div class="info-grid">
<div class="info-card">
<div class="info-label">Old Approach</div>
<div class="info-value red">Manual Hex Conversion</div>
</div>
<div class="info-card">
<div class="info-label">Modern Approach</div>
<div class="info-value green">HexFormat</div>
</div>
<div class="info-card">
<div class="info-label">Since JDK</div>
<div class="info-value accent">17</div>
</div>
<div class="info-card">
<div class="info-label">Difficulty</div>
<div class="info-value blue">intermediate</div>
</div>
</div>
<section class="bs-section">
<div class="section-label">JDK Support</div>
<div class="bs-card">
<div class="bs-feature-name">HexFormat</div>
<span class="baseline-badge widely">Available</span>
<p class="bs-desc">Widely available since JDK 17 LTS (Sept 2021)</p>
</div>
</section>
<section class="explanation">
<h2>How it works</h2>
<p>HexFormat provides bidirectional hex encoding/decoding for bytes, ints, and arrays. Configure delimiters, prefix, suffix, and case. No more manual formatting or parsing.</p>
</section>
<section class="related">
<h2>Related patterns</h2>
<div class="related-grid">
<a href="/date-formatting.html" class="tip-card">
<div class="tip-card-body">
<div class="tip-card-header">
<div class="tip-badges">
<span class="badge datetime">Date/Time</span>
<span class="badge beginner">beginner</span>
</div>
</div>
<h3>Date formatting</h3>
</div>
<div class="card-code">
<div class="card-code-layer old-layer">
<div class="mini-label">Pre-Java 8</div>
<pre class="code-text">// Not thread-safe!
SimpleDateFormat sdf =
new SimpleDateFormat("yyyy-MM-dd");
String formatted = sdf.format(date);
// Must synchronize for concurrent use</pre>
</div>
<div class="card-code-layer modern-layer">
<div class="mini-label">Java 8+</div>
<pre class="code-text">DateTimeFormatter fmt =
DateTimeFormatter.ofPattern(
"uuuu-MM-dd");
String formatted =
LocalDate.now().format(fmt);
// Thread-safe, immutable</pre>
</div>
<span class="hover-hint">Hover to see modern ➜</span>
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<span class="browser-support"><span class="dot"></span>JDK 8+</span>
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<div class="tip-badges">
<span class="badge datetime">Date/Time</span>
<span class="badge intermediate">intermediate</span>
</div>
</div>
<h3>Instant with nanosecond precision</h3>
</div>
<div class="card-code">
<div class="card-code-layer old-layer">
<div class="mini-label">Java 8</div>
<pre class="code-text">// Millisecond precision only
long millis =
System.currentTimeMillis();
// 1708012345678</pre>
</div>
<div class="card-code-layer modern-layer">
<div class="mini-label">Java 9+</div>
<pre class="code-text">// Microsecond/nanosecond precision
Instant now = Instant.now();
// 2025-02-15T20:12:25.678901234Z
long nanos = now.getNano();</pre>
</div>
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<span class="badge datetime">Date/Time</span>
<span class="badge beginner">beginner</span>
</div>
</div>
<h3>Duration and Period</h3>
</div>
<div class="card-code">
<div class="card-code-layer old-layer">
<div class="mini-label">Pre-Java 8</div>
<pre class="code-text">// How many days between two dates?
long diff = date2.getTime()
- date1.getTime();
long days = diff
/ (1000 * 60 * 60 * 24);
// ignores DST, leap seconds</pre>
</div>
<div class="card-code-layer modern-layer">
<div class="mini-label">Java 8+</div>
<pre class="code-text">long days = ChronoUnit.DAYS
.between(date1, date2);
Period period = Period.between(
date1, date2);
Duration elapsed = Duration.between(
time1, time2);</pre>
</div>
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